We flew to Alicante yesterday. A few points that may be of interest:-

The only document we uploaded to BA was the NHS fully vaccinated PDF certificate. Online checkin was straightforward.

On the flight face masks were handed out and expected to be worn.

On arrival at Alicante they have the self service passport reader machines. The long queue on the left was for adults with kids. There was a hidden shorter queue to the right (hidden due to longer queue on the left) that was for adults only and had a machine readable passport.

After the passport reading machines you have to go through the booths to have your passport stamped. No queue.

After the baggage hall when you exit there was a random COVID vaccination certificate check. We travelled as a family of four and two of us were asked to produce our certificate. Digital copy on phone was fine.

Great to be back in Spain after three years! Missed it.