I gave the PCR 68 hours before in case the flight was delayed. Got the result back in three hours. Straight away applied for the Thai pass and got it less than 12 hours later. Next month it will be approved straight away so no waiting
You can to get the PCR result in three hours if you pay extra. The pass was approved in 8 hours. Give yourself a little flexibility in the test. Our plane was a little late leaving London yesterday.
reading this I believe the pre departure PCR is still an option. I am at the airport now flying back but finding somewhere in the UK that still does the PCR was difficult.