If you are arriving in England, you must quarantine in a government approved hotel for 10 days. This is called ‘managed quarantine.
If you are arriving in Scotland, you must enter managed isolation and quarantine in an approved hotel for 10 days.

what you must do for details Since the 15 February It has not been possible to travel directly to Wales from a red list country.
Instead you must travel to England or Scotland, following their rules on managed quarantine

Once you have completed your 10 days of managed quarantine you can then travel on to Wales.

If you are arriving in Northern Ireland having been in or passed through a red list country you must also enter managed isolation and quarantine for 10 days.

Useful links :

Check https://www.go.sc/nhlications coronavirus cavid-19-international travel guarantine/pages/

Check https://www.nidirect.gov.uk/articles/coronavirus cavid. 19 countries and territories subject additional restrictions for details

Check bttps://gov.wales/exemptions self isolation Coronavirus-covid-19 html#section-60183 for details