Currently there are no entry requirements to Mexico.
Mexico is an Amber destination
UK Travel Requirements | Mexico is now on the UK Government's Amber list, which means you will need to quarantine on return to the UK. A pre-departure Covid-19 test before you return to the UK and two further tests when arriving home (days 2 and 8) will be required. Please see : https://www.gov.uk/guidance/red-amber-and-green-list-rules-for-entering-england#amber-list