With regards testing prior to return to UK from Spain. I understand PCR testing is advised but not mandatory, and rapid antigen tests should be ok still.

I assume it is BA that has the obligation to check the test? Be interested in hearing if anyone has experienced any push back at check in when presenting negative test proof via rapid antigen tests?

I have already booked rapid antigen tests for my return, so do not want to now have to book more expensive PCR tests if possible.

FYI my tests have been booked using the Malaga airport provider - http://travelcovidtestcenter.com/malaga

15 mins results for €25, but annoyingly completely non-refundable.