Test

Only a lateral flow/antigen test needed - you get the response quicker than pcr and it is cheaper.

The only PCR test that you need to book is the one for when you arrive into the UK. You must have it pre-booked before your flight, as when you fill in your UK passenger locator form it asks for the reference number of the test you have booked. As Peter says you only need to do a lateral flow test pre your flight, and it must be one where you get a fit to fly certificate, which they will check before your departure from Spain.

 Hope this helps