I gave ny OH some �5 stamps to use on a parcel he had to pist. He took it to the post office and the woman behind the counter had to check to see if they were real!! She'd never seen one!! LOL
Wasn't aware you could, Catron - but looking at the Royal mail site I see you are right.
They are certainly not standard stock at (smaller?) post offices - they used to be, but when printing labels came in they were removed from sale. I thought they had been withdrawn altogether but was obviously mistaken.