Under current UK COVID-19 restrictions, you must stay at home. You must not travel, including abroad, unless you have a legally permitted reason to do so. It is illegal to travel abroad for holidays and other leisure purposes. Check the rules that apply to you in England, Scotland, Wales and Northern Ireland.
If you intend to travel to England, Scotland, Wales, or Northern Ireland from abroad, including UK nationals returning home, 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.
If you are legally permitted to travel abroad, check our advice on your country of destination. Some other countries have closed borders, and may further restrict movement or bring in new rules including testing requirements with little warning.