I'd phone your GP back, they should be able to do a prescription and send it to the pharmacy.
I've just realised this thread it here when the last one locked me out.
I think the Government are between a rock and hard place but at the same time what I absolutely blame them for is not getting the vaccines in heavily populated areas done quickly enough.
To the poster wanting to visit Orkey, take an test and go. If I can spot German cars stoating round Lanarkshire you can go visit Orkney.
I hope I'm wrong but we could be in this a while yet.