Don’t believe the newspapers!
The rules differ for England, Scotland, Wales and Northern Ireland. Constantly check the official Government travel advice.
And always refer to the regulations of your destination country.
With all countries on returning you need proof of a negative coronavirus (Covid-19) test and a completed passenger locator form.
With the GREEN countries, in effect currently Gibraltar, Iceland, Israel and Portugal, there is no need to quarantine. For AMBER the requirement is to isolate for 10 days and be subject to test and trace. You cannot enter the UK if you have been in or through a country on the RED list unless you are British, Irish or you have the right to live in the UK. As a Brit you will need to quarantine for 10 days at an approved hotel and follow certain procedures.