Update travel advice callout boxes

This updates the copy for the callout boxes in line with new guidance.

app/views/content_items/_ireland_covid_travel_guidance.html.erb

@@ -4,7 +4,7 @@
   </strong>
 </p>
 <p class="govuk-body">
-  From 15 January, if you intend to <a href="/government/speeches/international-travel-update-11-january-2021">travel to England</a> or <a href="https://www.gov.scot/news/pre-departure-coronavirus-testing-update/">Scotland</a> from outside the Common Travel Area, including UK nationals returning home from travel abroad, you must provide evidence of a negative COVID-19 test result taken up to 3 days before departure. This testing requirement does not apply to travel from Ireland.
+  From 4am on 18 January, if you intend to travel to <a href="/guidance/coronavirus-covid-19-testing-for-people-travelling-to-england">England</a>, or from 4am on 15 January if you intend to travel to <a href="https://www.gov.scot/news/pre-departure-coronavirus-testing-update/">Scotland</a> from outside the Common Travel Area, including UK nationals returning home from travel abroad, you must provide evidence of a negative COVID-19 test result taken up to 3 days before departure. This testing requirement does not apply to travel from Ireland.
 </p>
 <p class="govuk-body">
   If you are legally permitted to travel, <a href="/guidance/travel-advice-novel-coronavirus">check our advice</a> for the country you are visiting. Some other countries have closed borders, and may further restrict movement or bring in new rules including testing requirements with little warning. Before you return to the UK you must <a href="/provide-journey-contact-details-before-travel-uk">provide your journey and contact details</a>. Also check if you need to <a href="/uk-border-control">self-isolate</a>.

app/views/content_items/travel_advice.html.erb

@@ -35,8 +35,7 @@
             Check the <a href="/guidance/national-lockdown-stay-at-home">rules that apply to you in England</a>, <a href="https://www.gov.scot/coronavirus-covid-19/">Scotland</a>, <a href="https://gov.wales/covid-19-alert-levels">Wales</a> and <a href="https://www.nidirect.gov.uk/articles/coronavirus-covid-19-regulations-guidance-what-restrictions-mean-you">Northern Ireland</a>.
           </p>
           <p class="govuk-body">
-            From 15 January, if you intend to <a href="/government/speeches/international-travel-update-11-january-2021">travel to England</a> or <a href="https://www.gov.scot/news/pre-departure-coronavirus-testing-update/">Scotland</a>, including UK nationals returning home from travel abroad, you must provide evidence of a negative COVID-19 test result taken up to 3 days before departure. If you do not comply (and you do not have a valid exemption) your airline or carrier may refuse you boarding and/or you may be fined on arrival. All other current entry requirements and restrictions continue to apply.
-          </p>
+            From 4am on 18 January, if you intend to travel to <a href="/guidance/coronavirus-covid-19-testing-for-people-travelling-to-england">England</a>, or from 4am on 15 January if you intend to travel to <a href="https://www.gov.scot/news/pre-departure-coronavirus-testing-update/">Scotland</a>, including UK nationals returning home from travel abroad, you must provide evidence of a negative COVID-19 test result taken up to 3 days before departure. If you do not comply (and you do not have a valid exemption) your airline or carrier may refuse you boarding and/or you may be fined on arrival. All other current entry requirements and restrictions continue to apply.
           <p class="govuk-body">
             If you are legally permitted to travel, <a href="/guidance/travel-advice-novel-coronavirus">check our advice</a> for the country you are visiting. Some other countries have closed borders, and may further restrict movement or bring in new rules including testing requirements with little warning. Before you return to the UK you must <a href="/provide-journey-contact-details-before-travel-uk">provide your journey and contact details</a>. Also check if you need to <a href="/uk-border-control">self-isolate</a>.
           </p>