This relates to travel from France but I got the info from here and the pharmacy were unsure as Antigen are now valid for 72 hours in France :shrug:
To avoid any hassle I went for the PCR as I was right on the limit of 24 hours for travel...
Concise and 100% what is required I think, although when I came back from France last month the Antigen was only valid for 24 hours and the PCR for 72 hours, has the Antigen validity been extended recently?