Business Travel News publishes here the two lists of countries where quarantine is usually no longer required when you return to the UK from 10 July.

If you fly from Scotland, Wales or Northern Ireland different rules apply. 

This is the Department for Transport listing.
www.gov.uk/guidance/coronavirus-covid-19-travel-corridors

The Foreign & Commonwealth Office advice on avoiding ‘all but essential’ travel is not identical but is the one that covers travel insurance validity.
www.gov.uk/guidance/coronavirus-covid-19-countries-and-territories-exempt-from-advice-against-all-but-essential-international-travel

Just to confuse matters you will still need to provide your contact information when you return to the UK, unless you fall into one of the categories on this list.
www.gov.uk/government/publications/coronavirus-covid-19-travellers-exempt-from-uk-border-rules/coronavirus-covid-19-travellers-exempt-from-uk-border-rules

It is a great pity that the daily news conferences no longer take place.  Surely a brave journalist would have questioned the minister where he and his family were taking their holiday this coming August, and for the advisors to answer too.  If not an MP should raise the question with the Prime Minister in Parliament at PMQ's.