48 hour test from Medicspot.
My wife has just got her test done this afternoon through a company called medicspot. They charge £150 (maybe plus another £30 to have your passport number on the form) and you can pre-order the kit on their website for collection (and drop-off) at one of their "hub" chemists.
Online said kit was sold out in Glasgow, so she went to the Edinburgh one and collected kit from chemist, sat in car, did the swab and then filled out some forms and handed it back into the chemist just before the 2pm cut-off. Result is due by 11pm tomorrow, just in time for a 6am Ryanair flight!
If you go down this route, ideally take a laptop with you. First, take a note of the order number - it is a hash followed by four digits and is on the original order confirmation.
Then you go to their website and fill in a form. This is separate from the paperwork with the test swab. Hence suggesting you take a laptop with you! Or phone your spouse! When it asks for the order number you don't put in the hash!
On the online form you also fill in the time you took the swab, this is the time from which the 72 hours starts ticking. That's why wife sat in the car outside the chemist at 1:30 to do the test so as she'd meet the 2pm cut-off.
Hopefully, the result will arrive "as guaranteed" before 11pm tomorrow!
If you decide to use them, this code gives me a tenner:
http://medicspot.refr.cc/martab