Through Chronomics (TUI partner), it was/is £60 for pre-flight PCR and Day 2, but you have to have booked through TUI. As a seasoned traveller you will probably know this, but just make sure you check the time period of when you should do the PCR test, some are 72 hours before departure and some 72 hours before arrival. Family of 4 were refused boarding on our flight to Kos from Manchester as they had taken their tests to early.
Results come through within 24 hours after dropping off at either a Royal Mail priority box or back to a pharmacy.