diff --git a/.gitignore b/.gitignore
index f6e2720e..f2d0b214 100644
--- a/.gitignore
+++ b/.gitignore
@@ -40,9 +40,10 @@ yarn-debug.log*
 /public/uploads
 
 ### Rails specific ###
+.byebug_history
 /public/system
 /coverage/
-/spec/tmp
+tmp
 
 # Ignore files specific to the development environment
 fc.json
diff --git a/.rubocop.yml b/.rubocop.yml
index 85503400..e0613b4c 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -16,113 +16,145 @@ Layout/LineLength:
     - config/**/*
     - test/**/*
 
-Metrics/ClassLength:
-  Exclude:
-    - test/**/*
-
-Metrics/BlockLength:
-  Max: 30
-  Exclude:
-    - test/**/*
-    - lib/tasks/**/*
+Layout/EmptyLinesAroundAttributeAccessor:
+  Enabled: true
 
-Metrics/MethodLength:
-  Exclude:
-    - lib/tasks/location.rake
+Layout/SpaceAroundMethodCallOperator:
+  Enabled: true
 
-Style/FormatStringToken:
-  Enabled: false
+Lint/DeprecatedOpenSSLConstant:
+  Enabled: true
 
-Rails/OutputSafety:
-  Exclude:
-    - app/presenters/*.rb
+Lint/DuplicateElsifCondition:
+  Enabled: true
 
-Style/HashEachMethods:
+Lint/MixedRegexpCaptureTypes:
   Enabled: true
 
-Style/HashTransformKeys:
+Lint/RaiseException:
   Enabled: true
 
-Style/HashTransformValues:
+Lint/StructNewOverride:
   Enabled: true
 
 Metrics/AbcSize:
   Exclude:
     - lib/tasks/location.rake
 
+Metrics/BlockLength:
+  Max: 30
+  Exclude:
+    - test/**/*
+    - lib/tasks/**/*
+
+Metrics/ClassLength:
+  CountAsOne: ['array', 'hash', 'heredoc', 'method_call']
+  Exclude:
+    - test/**/*
+
 Metrics/CyclomaticComplexity:
   Exclude:
     - lib/tasks/location.rake
 
-Layout/SpaceAroundMethodCallOperator:
+Metrics/MethodLength:
+  CountAsOne: ['array', 'hash', 'heredoc', 'method_call']
+  Exclude:
+    - lib/tasks/location.rake
+
+Rails/ActiveRecordCallbacksOrder:
   Enabled: true
-Layout/EmptyLinesAroundAttributeAccessor:
+
+Rails/FindById:
   Enabled: true
-Lint/DeprecatedOpenSSLConstant:
+
+Rails/I18nLocaleAssignment:
   Enabled: true
-Lint/MixedRegexpCaptureTypes:
+  Exclude:
+    - test/**/*
+Rails/Inquiry:
   Enabled: true
-Lint/RaiseException:
+
+Rails/MailerName:
   Enabled: true
-Lint/StructNewOverride:
+
+Rails/MatchRoute:
   Enabled: true
-Style/ExponentialNotation:
+
+Rails/NegateInclude:
   Enabled: true
-Style/RedundantFetchBlock:
+
+Rails/Pluck:
   Enabled: true
-Style/RedundantRegexpCharacterClass:
+
+Rails/PluckInWhere:
   Enabled: true
-Style/RedundantRegexpEscape:
+
+Rails/RenderInline:
   Enabled: true
-Style/SlicingWithRange:
+
+Rails/RenderPlainText:
   Enabled: true
-Lint/DuplicateElsifCondition:
+
+Rails/ShortI18n:
   Enabled: true
+
+Rails/WhereExists:
+  Enabled: true
+
+Rails/OutputSafety:
+  Exclude:
+    - app/presenters/*.rb
+
 Style/AccessorGrouping:
   Enabled: true
+
 Style/ArrayCoercion:
   Enabled: true
+
 Style/BisectedAttrAccessor:
   Enabled: true
+
 Style/CaseLikeIf:
   Enabled: true
-Style/HashAsLastArrayItem:
-  Enabled: true
-Style/HashLikeCase:
-  Enabled: true
-Style/RedundantAssignment:
-  Enabled: true
-Style/RedundantFileExtensionInRequire:
-  Enabled: true
-Rails/ActiveRecordCallbacksOrder:
-  Enabled: true
-Rails/FindById:
+
+Style/ExponentialNotation:
   Enabled: true
-Rails/Inquiry:
+
+Style/FormatStringToken:
+  Enabled: false
+
+Style/HashAsLastArrayItem:
   Enabled: true
-Rails/MailerName:
+
+Style/HashEachMethods:
   Enabled: true
-Rails/MatchRoute:
+
+Style/HashLikeCase:
   Enabled: true
-Rails/NegateInclude:
+
+Style/HashTransformKeys:
   Enabled: true
-Rails/Pluck:
+
+Style/HashTransformValues:
   Enabled: true
-Rails/PluckInWhere:
+
+Style/RedundantAssignment:
   Enabled: true
-Rails/RenderInline:
+
+Style/RedundantFetchBlock:
   Enabled: true
-Rails/RenderPlainText:
+
+Style/RedundantFileExtensionInRequire:
   Enabled: true
-Rails/ShortI18n:
+
+Style/RedundantRegexpCharacterClass:
   Enabled: true
-Rails/WhereExists:
+
+Style/RedundantRegexpEscape:
   Enabled: true
 
-Rails/I18nLocaleAssignment:
+Style/SlicingWithRange:
   Enabled: true
-  Exclude:
-    - test/**/*
 
 Style/OpenStructUse:
   Enabled: false
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4425c155..f39ae373 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,29 +2,71 @@
 
 ## 1.7.5 - 2024-08
 
+- (Jon) Exposed `instrument_internal_error(exception)` metric to the
+  `ExceptionsController` to provide a count of internal errors
+  [GH-142](https://github.com/epimorphics/hmlr-linked-data/issues/142)
+- (Jon) Added puma.stats to footer template in development environment only,
+  again as per the approach in the [`LR_Common_Styles`
+  gem](https://github.com/epimorphics/lr_common_styles/releases/tag/1.9.6)
+- (Jon) Adjusted footer `link_to` helpers to only appending the lang parameter
+  to the url only if it exists for "internal" links as per the approach in the
+  [`LR_Common_Styles`
+  gem](https://github.com/epimorphics/lr_common_styles/releases/tag/1.9.6)
+- (Jon) Adjusted fix for visual contrast in the location selection menu via
+  additional styling and updated 3rd-party element use specific to ticket
+  [GH-408](https://github.com/epimorphics/ukhpi/issues/408) alongside adding
+  missing aria-attributes required for assisted use
+- (Jon) Implements revised approach to page titles mirrored on other suite apps,
+  as well as fixes white space typo in some concatenated page titles
+- (Jon) Added `process_threads` guage to prometheus metrics alongside isolating
+  thread counts to specific status' as per the Rails thread documentation as
+  well as updating the approach to resolve
+  [GH-142](https://github.com/epimorphics/hmlr-linked-data/issues/142)
+- (Jon) Excluded prometheus metrics from the testing environment to reduce noise
+  in the logs
+- (Jon) Added `puma-metrics` gem to provide base metrics for the Puma web server
+- (Jon) Updated .rubocop.yml primarily reorganising the rules alphabetically as
+  well as adding `CountAsOne` to both `Metrics/ClassLength` and
+  `Metrics/MethodLength`; includes files with removed earlier disabling of said
+  rules!
+- (Jon) Updated `.gitignore` to include ignoring byebug history as well as sets
+  the tmp directory ignore to be anywhere, not just at the project root
+- (Bogdan) Fixed a bug where CSS was being applied to the wrong element
+  [GH-412](https://github.com/epimorphics/ukhpi/issues/412)
+- (Bogdan) Fixed type in aria-label text
+  [GH-416](https://github.com/epimorphics/ukhpi/issues/416)
 - (Dan) Adds message for screenreaders for guidance on how to use tables [Gh-405](https://github.com/epimorphics/ukhpi/issues/405)
 - (Dan) Fixed aria-label in compare locations form [GH-416](https://github.com/epimorphics/ukhpi/issues/416)
 - (Dan) Adds `aria-label` link attributes on the about page to SPARQL link
   [GH-413](https://github.com/epimorphics/ukhpi/issues/413)
-- (Bogdan) Fixed a bug where CSS was being applied to the wrong element [GH-412](https://github.com/epimorphics/ukhpi/issues/412)
+- (Bogdan) Fixed a bug where CSS was being applied to the wrong element 
+  [GH-412](https://github.com/epimorphics/ukhpi/issues/412)
+- (Bogdan) Fixed type in aria-label text [GH-416](https://github.com/epimorphics/ukhpi/issues/416)
 - (Bogdan) Fixed a duplicate character bug when selecting dates
-- (Bogdan) Added page titles for each individual view [GH-409](https://github.com/epimorphics/ukhpi/issues/409)
+- (Bogdan) Added page titles for each individual view
+  [GH-409](https://github.com/epimorphics/ukhpi/issues/409)
 - (Bogdan) Set correct values for `aria-label` link attributes on the about page
   [GH-413](https://github.com/epimorphics/ukhpi/issues/413)
-- (Bogdan) Increased contrast for compare location dropdowns [GH-412](https://github.com/epimorphics/ukhpi/issues/412)
+- (Bogdan) Increased contrast for compare location dropdowns
+  [GH-412](https://github.com/epimorphics/ukhpi/issues/412)
 - (Bogdan) Increased contrast for search location results, as well as when they
   are being focused [GH-412](https://github.com/epimorphics/ukhpi/issues/412)
 - (Bogdan) CSS Refactoring
-- (Bogdan) Fixed a bug where CSS was applied to the wrong element, causing search
-  location results to be displayed incorrectly
-- (Bogdan) Increased focusable area for close button on modal and hide graph button
-  [GH-411](https://github.com/epimorphics/ukhpi/issues/411)
-- (Bogdan) Increased contrast for search location input and map elements, as well
-  as all modal buttons [GH-408](https://github.com/epimorphics/ukhpi/issues/408)
-- (Bogdan) Increased contrast of modal warning message [GH-407](https://github.com/epimorphics/ukhpi/issues/407)
-- (Bogdan) Increased contrast for modal close button and body [GH-407](https://github.com/epimorphics/ukhpi/issues/407)
-- (Bogdan) Landing page links should now be more visible [GH-406](https://github.com/epimorphics/ukhpi/issues/406)
-- (Bogdan) Added alt text to application logo [GH-404](https://github.com/epimorphics/ukhpi/issues/404)
+- (Bogdan) Fixed a bug where CSS was applied to the wrong element, causing
+  search location results to be displayed incorrectly
+- (Bogdan) Increased focusable area for close button on modal and hide graph
+  button [GH-411](https://github.com/epimorphics/ukhpi/issues/411)
+- (Bogdan) Increased contrast for search location input and map elements, as
+  well as all modal buttons
+  [GH-408](https://github.com/epimorphics/ukhpi/issues/408)
+- (Bogdan) Increased contrast of modal warning message
+  [GH-407](https://github.com/epimorphics/ukhpi/issues/407)
+- (Bogdan) Increased contrast for modal close button and body
+  [GH-407](https://github.com/epimorphics/ukhpi/issues/407)
+- (Bogdan) Landing page links should now be more visible
+  [GH-406](https://github.com/epimorphics/ukhpi/issues/406)
+- (Bogdan) Added alt text to application logo
+  [GH-404](https://github.com/epimorphics/ukhpi/issues/404)
 
 ## 1.7.4 - 2024-04-19
 
diff --git a/Gemfile b/Gemfile
index 91c45ccc..e5c746ba 100644
--- a/Gemfile
+++ b/Gemfile
@@ -32,6 +32,7 @@ gem 'get_process_mem', '~> 0.2.7'
 gem 'http_accept_language'
 gem 'prometheus-client', '~> 4.0'
 gem 'puma'
+gem 'puma-metrics'
 gem 'rdf-turtle'
 gem 'rubocop-rails'
 gem 'sentry-rails', '~> 5.7'
diff --git a/Gemfile.lock b/Gemfile.lock
index d98662c5..c69f14bf 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -183,7 +183,6 @@ GEM
     matrix (0.4.2)
     method_source (1.0.0)
     mini_mime (1.1.2)
-    mini_portile2 (2.8.4)
     minitest (5.18.1)
     minitest-rails (6.1.0)
       minitest (~> 5.10)
@@ -196,8 +195,7 @@ GEM
     mocha (1.13.0)
     multipart-post (2.3.0)
     nio4r (2.5.9)
-    nokogiri (1.13.10)
-      mini_portile2 (~> 2.8.0)
+    nokogiri (1.13.10-x86_64-darwin)
       racc (~> 1.4)
     oj (3.14.2)
     parallel (1.22.1)
@@ -207,6 +205,9 @@ GEM
     public_suffix (5.0.3)
     puma (6.3.1)
       nio4r (~> 2.0)
+    puma-metrics (1.2.5)
+      prometheus-client (>= 0.10)
+      puma (>= 5.0)
     racc (1.7.1)
     rack (2.2.7)
     rack-proxy (0.7.6)
@@ -361,7 +362,7 @@ GEM
       railties
 
 PLATFORMS
-  ruby
+  x86_64-darwin-21
 
 DEPENDENCIES
   byebug
@@ -388,6 +389,7 @@ DEPENDENCIES
   oj (= 3.14.2)
   prometheus-client (~> 4.0)
   puma
+  puma-metrics
   rails (~> 6.0)
   rdf-turtle
   rubocop
diff --git a/app/assets/stylesheets/_data-view-download.scss b/app/assets/stylesheets/_data-view-download.scss
index c8e09e53..30825f78 100644
--- a/app/assets/stylesheets/_data-view-download.scss
+++ b/app/assets/stylesheets/_data-view-download.scss
@@ -13,14 +13,32 @@
     text-decoration: none;
   }
 
-  &__button, &__button:visited, &__button:link, &__button:focus, &__button:link:focus {
-    color: white;
-    background-color: $dark-blue;
+  &__button{
+    &:visited, &:link {
+      color: white;
+      background-color: $dark-blue;
+      &:hover, &:focus, &:visited {
+        color: white;
+        background-color: $dark-blue-hover;
+      }
+    }
   }
 }
 
 .c-compare__download-link {
   @extend .button;
+  color: white;
   background-color: $dark-blue;
   font-size: 1.5rem;
+  &:hover, &:focus, &:visited {
+    color: white;
+    background-color: $dark-blue-hover;
+  }
+}
+
+.c-compare__print-link {
+  color: $dark-blue;
+  &:hover, &:focus, &:visited {
+    color: $dark-blue-hover;
+  }
 }
diff --git a/app/assets/stylesheets/_element-rails.scss b/app/assets/stylesheets/_element-rails.scss
index d1c3132c..c9f1d6a9 100644
--- a/app/assets/stylesheets/_element-rails.scss
+++ b/app/assets/stylesheets/_element-rails.scss
@@ -20,8 +20,8 @@
 }
 
 .el-table .cell {
-  word-break: normal;
   -ms-word-break: normal;
+  word-break: normal;
 }
 
 .el-button--default {
@@ -30,6 +30,11 @@
 
 .el-button--primary {
   background-color: $dark-blue;
+  border-color: $dark-blue;
+  &:any-link, &:focus, &:hover {
+    background-color: $dark-blue-hover;
+    border-color: $dark-blue-hover;
+  }
 }
 
 .el-date-editor {
@@ -57,6 +62,7 @@ table.el-month-table {
     color: white;
   }
   &.hover:not(.selected) {
-    background-color: #e6e6e6;
+    background-color: $dark-blue-hover;
+    color: white;
   }
 }
diff --git a/app/assets/stylesheets/_gov_uk.scss b/app/assets/stylesheets/_gov_uk.scss
index a1be390f..fef7be08 100644
--- a/app/assets/stylesheets/_gov_uk.scss
+++ b/app/assets/stylesheets/_gov_uk.scss
@@ -17,8 +17,12 @@
 @import 'elements/reset';
 @import "elements/helpers";                       // Helper functions and classes
 
+$govuk-brand-colour:	#1d70b8;
+$govuk-brand-hover-colour:	#003078;
+
 $grey-8: #f0f0f0;
-$dark-blue: #003078;
+$dark-blue: $govuk-brand-colour;
+$dark-blue-hover: $govuk-brand-hover-colour;
 @import "elements/govuk-template-base";                       // HTML elements, set by the GOV.UK template
 
 
diff --git a/app/assets/stylesheets/_leaflet-rrose.scss b/app/assets/stylesheets/_leaflet-rrose.scss
index 5a93df15..41bd2a1a 100644
--- a/app/assets/stylesheets/_leaflet-rrose.scss
+++ b/app/assets/stylesheets/_leaflet-rrose.scss
@@ -103,9 +103,9 @@ a.leaflet-rrose-close-button:hover {
 .leaflet-rrose-content-wrapper, .leaflet-rrose-tip {
     background: white;
 
-    box-shadow: 0 3px 10px #888;
     -moz-box-shadow: 0 3px 10px #888;
     -webkit-box-shadow: 0 3px 14px #999;
+    box-shadow: 0 3px 10px #888;
 }
 
 .leaflet-rrose-content-wrapper {
diff --git a/app/assets/stylesheets/_lr-common.scss b/app/assets/stylesheets/_lr-common.scss
index cd3fd652..c814c092 100644
--- a/app/assets/stylesheets/_lr-common.scss
+++ b/app/assets/stylesheets/_lr-common.scss
@@ -38,8 +38,8 @@ ol.numbered {
 
 input[type=checkbox],
 input[type=radio] {
-  transform: scale(1.5);
   -webkit-transform: scale(1.5);
+  transform: scale(1.5);
 }
 
 /* objects */
@@ -261,3 +261,4 @@ input[type=radio] {
 :focus, a:focus {
   outline: 2px solid $focus-colour !important;
 }
+
diff --git a/app/assets/stylesheets/a11y.scss b/app/assets/stylesheets/a11y.scss
new file mode 100644
index 00000000..0acb004c
--- /dev/null
+++ b/app/assets/stylesheets/a11y.scss
@@ -0,0 +1,101 @@
+/* Created in 2024-08 accessibility review ~ JRH */
+$govuk-brand-colour:	#1d70b8;
+$govuk-brand-hover-colour:	#003078;
+$govuk-brand-disabled-colour: lighten( $govuk-brand-colour, 40% );
+
+
+@mixin disabled-button {
+  color: #606266;
+  background-color: $govuk-brand-disabled-colour;
+  border-color: $govuk-brand-disabled-colour;
+  opacity: 0.4;
+  cursor: not-allowed;
+}
+
+@mixin hidden-radio {
+  opacity: 0;
+  outline: 0;
+  position: absolute;
+  z-index: -1;
+}
+
+button,
+.button{
+  &.el-button {
+    &--primary{
+      background-color: $govuk-brand-colour;
+      border-color: $govuk-brand-colour;
+      &:hover,
+      &:focus {
+        background-color: $govuk-brand-hover-colour;
+        border-color: $govuk-brand-hover-colour;
+      }
+      &.is-disabled {
+        @include disabled-button;
+        &:active,
+        &:focus,
+        &:hover {
+          @include disabled-button;
+        }
+      }
+    }
+  }
+}
+
+div {
+  &.el-radio-group {
+    &[role="radiogroup"] {
+      [role="radio"]{
+        &.el-radio-button {
+          position: relative;
+          display: inline-block;
+          width: 100%;
+          outline: 0;
+          width: 100%;
+          margin: 0;
+          padding: 0;
+          &.is-checked {
+            .el-radio__label {
+              color: #FFF;
+              background-color: $govuk-brand-colour;
+            }
+          }
+
+          .el-radio__input {
+            @include hidden-radio;
+            .el-radio__inner{
+              display: none;
+            }
+          }
+          .el-radio__label {
+            width: 100%;
+            border: 0;
+            border-radius: 0;
+            color: #000000;
+            display: inline-block;
+            line-height: 2.0;
+            text-align: center;
+            padding: 0.75rem 1.4rem;
+            font-size: calc(1.0rem + 0.2vw); // maintain text size relative to viewport width
+            background-color: #FFF;
+            font-weight: 500;
+            text-align: center;
+            box-sizing: border-box;
+              &:hover, &:focus, &:visited {
+                background-color: $govuk-brand-hover-colour;
+                color: #FFF;
+              }
+              &:active {
+                background-color: $govuk-brand-hover-colour;
+                color: $govuk-brand-colour;
+              }
+          }
+          [aria-hidden="true"] {
+            @include hidden-radio;
+          }
+        }
+      }
+    }
+  }
+}
+
diff --git a/app/assets/stylesheets/application.scss b/app/assets/stylesheets/application.scss
index 5672fe70..a135d04d 100644
--- a/app/assets/stylesheets/application.scss
+++ b/app/assets/stylesheets/application.scss
@@ -24,4 +24,5 @@
   'ukhpi-location-select',
   'actions',
   'skip_to_main',
-  'cookie-banner';
+  'cookie-banner',
+  'a11y';
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index c2acf040..34285f77 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -6,9 +6,30 @@ class ApplicationController < ActionController::Base
   # For APIs, you may want to use :null_session instead.
   protect_from_forgery with: :exception
 
-  before_action :set_locale, :change_default_caching_policy
+  before_action :set_locale
+  before_action :change_default_caching_policy
 
   around_action :log_request_result
+
+  # Set the user's preferred locale. An explicit locale set via
+  # the URL param `lang` is preeminent, otherwise we look to the
+  # user's preferred language specified via browser headers
+  def set_locale
+    user_locale = params['lang']
+    user_locale ||= http_accept_language.compatible_language_from(I18n.available_locales)
+
+    I18n.locale = user_locale if Rails.application.config.welsh_language_enabled
+  end
+
+  # * Set cache control headers for HMLR apps to be public and cacheable
+  # * UHPI needs to be shorter to avoid delay (in users cache) on the
+  # * publication deadline so it is set for 2 minutes (120 seconds)
+  # Sets the default `Cache-Control` header for all requests,
+  # unless overridden in the action
+  def change_default_caching_policy
+    expires_in 2.minutes, public: true, must_revalidate: true if Rails.env.production?
+  end
+
   def log_request_result
     start = Process.clock_gettime(Process::CLOCK_MONOTONIC, :microsecond)
     yield
@@ -18,7 +39,7 @@ def log_request_result
 
   private
 
-  # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
+  # rubocop:disable Metrics/AbcSize
   def detailed_request_log(duration)
     env = request.env
 
@@ -38,7 +59,7 @@ def detailed_request_log(duration)
 
     case response.status
     when 500..599
-      log_fields[:message] = env['action_dispatch.exception']
+      log_fields[:message] = env['action_dispatch.exception'].to_s
       Rails.logger.error(JSON.generate(log_fields))
     when 400..499
       Rails.logger.warn(JSON.generate(log_fields))
@@ -46,25 +67,14 @@ def detailed_request_log(duration)
       Rails.logger.info(JSON.generate(log_fields))
     end
   end
-  # rubocop:enable Metrics/MethodLength, Metrics/AbcSize
-
-  # Set the user's preferred locale. An explicit locale set via
-  # the URL param `lang` is preeminent, otherwise we look to the
-  # user's preferred language specified via browser headers
-  def set_locale
-    user_locale =
-      params['lang'] ||
-      http_accept_language.compatible_language_from(I18n.available_locales)
+  # rubocop:enable Metrics/AbcSize
 
-    I18n.locale = user_locale if Rails.application.config.welsh_language_enabled
-  end
-
-  # * Set cache control headers for HMLR apps to be public and cacheable
-  # * UHPI needs to be shorter to avoid delay (in users cache) on the
-  # * publication deadline so it is set for 2 minutes (120 seconds)
-  # Set the default `Cache-Control` header for all requests,
-  # unless overridden in the action
-  def change_default_caching_policy
-    expires_in 2.minutes, public: true, must_revalidate: true if Rails.env.production?
+  # Notify subscriber(s) of an internal error event with the payload of the
+  # exception once done
+  # @param [Exception] exp the exception that caused the error
+  # @return [ActiveSupport::Notifications::Event] provides an object-oriented
+  # interface to the event
+  def instrument_internal_error(exception)
+    ActiveSupport::Notifications.instrument('internal_error.application', exception: exception)
   end
 end
diff --git a/app/controllers/browse_controller.rb b/app/controllers/browse_controller.rb
index 0511a785..8b7f2a3e 100644
--- a/app/controllers/browse_controller.rb
+++ b/app/controllers/browse_controller.rb
@@ -3,7 +3,7 @@
 # Controller for the main user experience of browsing the UKHPI statistics.
 # Usually the primary interaction will be via JavaScript and XHR, but we also
 # support non-JS access by setting browse preferences in the `edit` action.
-class BrowseController < ApplicationController # rubocop:disable Metrics/ClassLength
+class BrowseController < ApplicationController
   layout 'webpack_application'
 
   def show
@@ -128,7 +128,7 @@ def view_result(view_state)
     }.merge(new_params))
   end
 
-  def render_request_error(user_selections, status) # rubocop:disable Metrics/MethodLength
+  def render_request_error(user_selections, status)
     respond_to do |format|
       @view_state = { user_selections: user_selections }
       request_status = status == 400 ? :bad_request : :internal_server_error
diff --git a/app/controllers/compare_controller.rb b/app/controllers/compare_controller.rb
index a66da0ca..4998baf9 100644
--- a/app/controllers/compare_controller.rb
+++ b/app/controllers/compare_controller.rb
@@ -31,7 +31,7 @@ def render_print
     render 'compare/print', layout: 'print'
   end
 
-  def perform_query(user_compare_selections) # rubocop:disable Metrics/MethodLength
+  def perform_query(user_compare_selections)
     query_results = {}
     base_selection = UserSelections.new(
       __safe_params: {
diff --git a/app/controllers/exceptions_controller.rb b/app/controllers/exceptions_controller.rb
index 8258309f..11c20945 100644
--- a/app/controllers/exceptions_controller.rb
+++ b/app/controllers/exceptions_controller.rb
@@ -10,6 +10,8 @@ def render_error
     status_code = ActionDispatch::ExceptionWrapper.new(env, exception).status_code
 
     sentry_code = maybe_report_to_sentry(exception, status_code)
+    # add the exception to the prometheus metrics
+    instrument_internal_error(exception)
 
     render :error_page,
            locals: { status: status_code, sentry_code: sentry_code },
diff --git a/app/javascript/components/compare-locations.vue b/app/javascript/components/compare-locations.vue
index e3224edd..41d8a323 100644
--- a/app/javascript/components/compare-locations.vue
+++ b/app/javascript/components/compare-locations.vue
@@ -10,7 +10,8 @@
               :key='item.slug'
               :label='item.label'
               :value='item.slug'
-              :disabled='isDisabledIndicator(item.slug)'>
+              :disabled='isDisabledIndicator(item.slug)'
+              :aria-disabled='isDisabledIndicator(item.slug)'>
             </el-option>
           </el-select>
         </label>
@@ -26,7 +27,8 @@
                 :key='item.slug'
                 :label='item.label'
                 :value='item.slug'
-                :disabled='isDisabledStatistic(item.slug)'>
+                :disabled='isDisabledStatistic(item.slug)'
+                :aria-disabled='isDisabledStatistic(item.slug)'>
               </el-option>
             </el-option-group>
           </el-select>
diff --git a/app/javascript/components/select-location.vue b/app/javascript/components/select-location.vue
index 72694eda..36e3aa6e 100644
--- a/app/javascript/components/select-location.vue
+++ b/app/javascript/components/select-location.vue
@@ -70,12 +70,12 @@
                 {{ $t("js.location.show_on_map") }}
               </div>
               <nav aria-label="show location type">
-                <el-radio-group v-model='locationType'>
-                  <el-radio-button label='country'>{{ $t("js.location.type_countries") }}</el-radio-button>
-                  <el-radio-button label='la'>{{ $t("js.location.type_las") }}</el-radio-button>
-                  <el-radio-button label='region'>{{ $t("js.location.type_regions_england") }}</el-radio-button>
-                  <el-radio-button label='county'>{{ $t("js.location.type_counties_england") }}</el-radio-button>
-                </el-radio-group>
+                <div role="radiogroup" class="el-radio-group">
+                  <el-radio class="el-radio-button" name="locationType" v-model='locationType' :aria-label='$t("js.location.type_countries")' label='country'>{{ $t("js.location.type_countries") }}</el-radio>
+                  <el-radio class="el-radio-button" name="locationType" v-model='locationType' :aria-label='$t("js.location.type_las")' label='la'>{{ $t("js.location.type_las") }}</el-radio>
+                  <el-radio class="el-radio-button" name="locationType" v-model='locationType' :aria-label='$t("js.location.type_regions_england")' label='region'>{{ $t("js.location.type_regions_england") }}</el-radio>
+                  <el-radio class="el-radio-button" name="locationType" v-model='locationType' :aria-label='$t("js.location.type_counties_england")' label='county'>{{ $t("js.location.type_counties_england") }}</el-radio>
+                </div>
               </nav>
             </div>
           </div>
@@ -87,6 +87,8 @@
             type='primary'
             @click='onSaveChanges'
             :disabled='!allowConfirm'
+            :aria-disabled='!allowConfirm'
+            :aria-label='$t("js.action.confirm")'
           >{{ $t('js.action.confirm') }}</el-button>
         </span>
       </el-dialog>
diff --git a/app/models/concerns/cube_data_model/cube_measure.rb b/app/models/concerns/cube_data_model/cube_measure.rb
index 99ed8a96..d6e7c827 100644
--- a/app/models/concerns/cube_data_model/cube_measure.rb
+++ b/app/models/concerns/cube_data_model/cube_measure.rb
@@ -33,7 +33,7 @@ def decimal_range?
       range.include?(RDF::XSD.decimal)
     end
 
-    def unit_type # rubocop:disable Metrics/MethodLength
+    def unit_type
       if scalar?
         :scalar
       elsif percentage?
diff --git a/app/models/data_view.rb b/app/models/data_view.rb
index 52e24037..f2844e46 100644
--- a/app/models/data_view.rb
+++ b/app/models/data_view.rb
@@ -7,7 +7,7 @@
 # a view of the  `averagePrice` indicator, together with the relevant dates,
 # location and other options, and access to the underlying data, to enable
 # the renderer to draw the display
-class DataView # rubocop:disable Metrics/ClassLength
+class DataView
   include Rails.application.routes.url_helpers
 
   attr_reader :user_selections, :query_result, :indicator, :theme
diff --git a/app/models/latest_values_command.rb b/app/models/latest_values_command.rb
index 965bdcc3..aaa43dad 100644
--- a/app/models/latest_values_command.rb
+++ b/app/models/latest_values_command.rb
@@ -14,7 +14,7 @@ def perform_query(service = nil)
 
   private
 
-  def service_api(service) # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
+  def service_api(service) # rubocop:disable Metrics/AbcSize
     service || dataset(:ukhpi)
   rescue Faraday::ConnectionFailed => e
     Rails.logger.error { 'Failed to connect to UK HPI ' }
@@ -33,7 +33,7 @@ def service_api(service) # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
     nil
   end
 
-  def run_query(hpi) # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
+  def run_query(hpi) # rubocop:disable Metrics/AbcSize
     success = true
     query = add_date_range_constraint(base_query)
     query = add_location_constraint(query)
diff --git a/app/models/user_compare_selections.rb b/app/models/user_compare_selections.rb
index 8f1a693d..f2323149 100644
--- a/app/models/user_compare_selections.rb
+++ b/app/models/user_compare_selections.rb
@@ -78,7 +78,7 @@ def search?
 
   delegate :to_h, to: :params
 
-  def as_json # rubocop:disable Metrics/MethodLength, Metrics/AbcSize
+  def as_json # rubocop:disable Metrics/AbcSize
     {
       from: { date: from_date }.to_json,
       to: { date: to_date }.to_json,
diff --git a/app/models/user_selections.rb b/app/models/user_selections.rb
index 53300b5f..e8fc2af1 100644
--- a/app/models/user_selections.rb
+++ b/app/models/user_selections.rb
@@ -8,7 +8,7 @@
 # standard set of statistics is presented if there is no information in the
 # user parameters yet. This functionality combines the previous
 # `models/UserPreferences` and `presenters/Aspects`
-class UserSelections # rubocop:disable Metrics/ClassLength
+class UserSelections
   include UserChoices
   include UserSelectionValidations
   include UserLanguage
diff --git a/app/presenters/compare_locations_presenter.rb b/app/presenters/compare_locations_presenter.rb
index 09038185..509869df 100644
--- a/app/presenters/compare_locations_presenter.rb
+++ b/app/presenters/compare_locations_presenter.rb
@@ -4,7 +4,7 @@
 
 # Presenter class that encapsulates the behaviour of mapping the user-selections
 # to side-by-side comparisons for different areas
-class CompareLocationsPresenter # rubocop:disable Metrics/ClassLength
+class CompareLocationsPresenter
   include I18n
   include LocationsTable
 
@@ -25,7 +25,7 @@ def initialize(user_compare_selections, query_results)
   delegate :as_json, to: :user_compare_selections
   delegate :selected_locations, to: :user_compare_selections
 
-  def headline_summary # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
+  def headline_summary # rubocop:disable Metrics/AbcSize
     ind = I18n.t("indicator.#{indicator.slug}")
     stat = I18n.t("statistic.#{statistic.label_key}").downcase
     from = I18n.l(user_compare_selections.from_date, format: '%B %Y')
diff --git a/app/presenters/download_presenter.rb b/app/presenters/download_presenter.rb
index 511cc377..f69a57e8 100644
--- a/app/presenters/download_presenter.rb
+++ b/app/presenters/download_presenter.rb
@@ -116,7 +116,7 @@ def all_themes
     ukhpi.themes.values.map(&:slug)
   end
 
-  def sort_results_by_date_and_location # rubocop:disable Metrics/MethodLength
+  def sort_results_by_date_and_location
     @results.sort! do |result0, result1|
       date0 = result0['ukhpi:refMonth']['@value']
       date1 = result1['ukhpi:refMonth']['@value']
diff --git a/app/presenters/landing_state.rb b/app/presenters/landing_state.rb
index 04b5e02c..7cdf0155 100644
--- a/app/presenters/landing_state.rb
+++ b/app/presenters/landing_state.rb
@@ -72,7 +72,7 @@ def to_value(val)
     DataServicesApi::Value.new(val.symbolize_keys)
   end
 
-  def format_percentage(change) # rubocop:disable Metrics/MethodLength
+  def format_percentage(change)
     if change == 'unknown'
       change
     elsif change.zero?
diff --git a/app/presenters/print_presenter.rb b/app/presenters/print_presenter.rb
index 6e9d5e61..966b5acc 100644
--- a/app/presenters/print_presenter.rb
+++ b/app/presenters/print_presenter.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 # A presenter for the printable view, based on the download view presenter
-class PrintPresenter < DownloadPresenter # rubocop:disable Metrics/ClassLength
+class PrintPresenter < DownloadPresenter
   include ActionView::Helpers::NumberHelper
 
   PRINT_COLUMNS = [
@@ -120,7 +120,7 @@ def user_selection_columns
 
   # @return An array of the given statistic paired with the currently selected
   # indicators
-  def statistic_indicator_columns(stat) # rubocop:disable Metrics/MethodLength
+  def statistic_indicator_columns(stat)
     selected_indicators.map do |ind|
       DownloadColumn.new(
         ind: ind,
diff --git a/app/subscribers/action_dispatch_prometheus_subscriber.rb b/app/subscribers/action_dispatch_prometheus_subscriber.rb
index 5f02b5e0..8e0e428a 100644
--- a/app/subscribers/action_dispatch_prometheus_subscriber.rb
+++ b/app/subscribers/action_dispatch_prometheus_subscriber.rb
@@ -4,11 +4,57 @@
 class ActionDispatchPrometheusSubscriber < ActiveSupport::Subscriber
   attach_to :action_dispatch
 
-  def request(_event)
+  # rubocop:disable Metrics/AbcSize
+  def process_action(_event)
     mem = GetProcessMem.new
-
     Prometheus::Client.registry
                       .get(:memory_used_mb)
                       .set(mem.mb)
+    # description: 'Thread is aborting'
+    Prometheus::Client.registry
+                      .get(:process_threads)
+                      .set(
+                        Thread.list.select { |thread| thread.status == 'aborting' }.count,
+                        labels: {
+                          status: 'aborting'
+                        }
+                      )
+    # description: 'Thread is sleeping or waiting on I/O'
+    Prometheus::Client.registry
+                      .get(:process_threads)
+                      .set(
+                        Thread.list.select { |thread| thread.status == 'sleep' }.count,
+                        labels: {
+                          status: 'sleep'
+                        }
+                      )
+    # description: 'Thread is executing'
+    Prometheus::Client.registry
+                      .get(:process_threads)
+                      .set(
+                        Thread.list.select { |thread| thread.status == 'run' }.count,
+                        labels: {
+                          status: 'run'
+                        }
+                      )
+    # description: 'Thread is terminated normally'
+    Prometheus::Client.registry
+                      .get(:process_threads)
+                      .set(
+                        Thread.list.select { |thread| thread.status == false }.count,
+                        labels: {
+                          status: 'false'
+                        }
+                      )
+    # description: 'Thread is terminated with an exception'
+    Prometheus::Client.registry
+                      .get(:process_threads)
+                      .set(
+                        Thread.list.select { |thread| thread.status.nil? }.count,
+                        labels: {
+                          status: 'nil'
+                        }
+                      )
   end
+  # rubocop:enable Metrics/AbcSize
 end
diff --git a/app/subscribers/api_prometheus_subscriber.rb b/app/subscribers/api_prometheus_subscriber.rb
index 7b8b8678..f2a54a8d 100644
--- a/app/subscribers/api_prometheus_subscriber.rb
+++ b/app/subscribers/api_prometheus_subscriber.rb
@@ -4,7 +4,7 @@
 class ApiPrometheusSubscriber < ActiveSupport::Subscriber
   attach_to :api
 
-  def response(event) # rubocop:disable Metrics/MethodLength
+  def response(event)
     response = event.payload[:response]
     duration = event.payload[:duration]
 
diff --git a/app/views/changelog/_changelog_cy.html.haml b/app/views/changelog/_changelog_cy.html.haml
index d3fdc994..c671b038 100644
--- a/app/views/changelog/_changelog_cy.html.haml
+++ b/app/views/changelog/_changelog_cy.html.haml
@@ -2,7 +2,7 @@
 
 %section#main.c-changelog
   %h1.heading-large
-    = I18n.t('common.header.app_title') + " : " + yield(:title)
+    = "#{I18n.t('common.header.app_title')}: #{yield(:title)}"
 
   %h2.heading-medium Ebrill 2023 &ndash; Newidiadau i ddaearyddiaeth awdurdodau lleol yn Lloegr
 
diff --git a/app/views/changelog/_changelog_en.html.haml b/app/views/changelog/_changelog_en.html.haml
index 39a7f846..f34b9217 100644
--- a/app/views/changelog/_changelog_en.html.haml
+++ b/app/views/changelog/_changelog_en.html.haml
@@ -2,7 +2,7 @@
 
 %section#main.c-changelog
   %h1.heading-large
-    = I18n.t('common.header.app_title') + " : " + yield(:title)
+    = "#{I18n.t('common.header.app_title')}: #{yield(:title)}"
 
   %h2.heading-medium April 2023 &ndash; Changes to local authority geography in England
 
diff --git a/app/views/common/_footer.html.haml b/app/views/common/_footer.html.haml
index 6dcae841..2edd6210 100644
--- a/app/views/common/_footer.html.haml
+++ b/app/views/common/_footer.html.haml
@@ -16,9 +16,9 @@
             %a{:href => "https://www.gov.uk/land-registry-public-data"}
               = t('common.footer.public_data')
           %li.u-print-hidden
-            = link_to(t('common.footer.accessibility'), "#{Rails.application.config.accessibility_document_path}?lang=#{I18n.locale}")
+            = link_to(t('common.footer.accessibility'),"#{Rails.application.config.accessibility_document_path}#{"?lang=#{I18n.locale}" if params[:lang].present?}")
           %li.u-print-hidden
-            = link_to(t('common.footer.privacy'), "#{Rails.application.config.privacy_document_path}?lang=#{I18n.locale}")
+            = link_to(t('common.footer.privacy'),"#{Rails.application.config.privacy_document_path}#{"?lang=#{I18n.locale}" if params[:lang].present?}")
         .ogl.open-government-licence
           %p.logo.u-print-hidden
             %a{href: t('common.footer.ogl_url'), rel:"license"}
@@ -29,3 +29,8 @@
         %p.u-muted--footer
           = t('common.footer.application_release')
           = Version::VERSION
+    - if Rails.env.development?
+      %pre
+        [puma stats:
+        = JSON.pretty_generate(JSON.parse(Puma.stats, symbolize_names: true))
+        , time: #{Time.now}]
diff --git a/app/views/compare/show.html.haml b/app/views/compare/show.html.haml
index 0cf1ebed..f4bcaeba 100644
--- a/app/views/compare/show.html.haml
+++ b/app/views/compare/show.html.haml
@@ -4,7 +4,7 @@
   .column-full
     %article.c-compare
       %h1.o-heading--2
-        = t('compare.show.heading')
+        = yield(:title)
       %p.u-muted
         = t('compare.show.prompt')
 
diff --git a/app/views/doc/_about_ukhpi_cy.html.haml b/app/views/doc/_about_ukhpi_cy.html.haml
index 64c028e7..33ad83ef 100644
--- a/app/views/doc/_about_ukhpi_cy.html.haml
+++ b/app/views/doc/_about_ukhpi_cy.html.haml
@@ -1,7 +1,7 @@
 = content_for(:title, "Am")
 
 %h1.heading-large
-  = I18n.t('common.header.app_title') + " : " + yield(:title)
+  = "#{I18n.t('common.header.app_title')}: #{yield(:title)}"
 
 %h2.heading-medium
   Beth sydd wedi ei gynnwys yn Set Ddata’r Mynegai Prisiau Tai?
diff --git a/app/views/doc/_about_ukhpi_en.html.haml b/app/views/doc/_about_ukhpi_en.html.haml
index 3de4af77..9c841caa 100644
--- a/app/views/doc/_about_ukhpi_en.html.haml
+++ b/app/views/doc/_about_ukhpi_en.html.haml
@@ -1,7 +1,7 @@
 = content_for(:title, "About")
 
 %h1.heading-large
-  = I18n.t('common.header.app_title') + " : " + yield(:title)
+  = "#{I18n.t('common.header.app_title')}: #{yield(:title)}"
 
 %h2.heading-medium
   What does the House Price Index Dataset consist of?
diff --git a/config.ru b/config.ru
index 841c9832..b88c1e24 100644
--- a/config.ru
+++ b/config.ru
@@ -6,11 +6,13 @@ require_relative 'config/environment'
 
 require ::File.expand_path('config/environment', __dir__)
 
-require 'prometheus/middleware/collector'
-require 'prometheus/middleware/exporter'
+unless Rails.env.test?
+  require 'prometheus/middleware/collector'
+  require 'prometheus/middleware/exporter'
 
-use Prometheus::Middleware::Collector
-use Prometheus::Middleware::Exporter
+  use Prometheus::Middleware::Collector
+  use Prometheus::Middleware::Exporter
+end
 
 if ENV['RAILS_ENV'] == 'production'
   map Rails.application.config.relative_url_root || '/' do
diff --git a/config/initializers/prometheus.rb b/config/initializers/prometheus.rb
index c802544b..c8c06056 100644
--- a/config/initializers/prometheus.rb
+++ b/config/initializers/prometheus.rb
@@ -35,6 +35,13 @@
   docstring: 'Process memory usage in mb'
 )
 
+prometheus.gauge(
+  :process_threads,
+  docstring: 'The number of process threads, labelled by status',
+  labels: [:status],
+  preset_labels: { status: 'total' }
+)
+
 # Prometheus histograms
 prometheus.histogram(
   :api_response_times,
diff --git a/test/services/query_command_test.rb b/test/services/query_command_test.rb
index 90999250..b3c53a8c 100644
--- a/test/services/query_command_test.rb
+++ b/test/services/query_command_test.rb
@@ -10,7 +10,7 @@ def query(query)
   end
 end
 
-def validate_json(json) # rubocop:disable Metrics/MethodLength
+def validate_json(json)
   _(json).must_match_json_expression(
     '@and':
     [