Question Author
I've got to the bottom of one of them - the one with the eight stamps on. It wasn't a quiz request after all, but the envelope would have felt quite fat, so I guess whoever opened it thought they might find money inside. They would have been disappointed on that particular occasion!
Still leaves the other one, which is a white envelope and shows the imprint of a �1 coin, so not yours, candled. I recognise the surname, so feel pretty sure I've sent yours off. Hope you get it soon.
I was wondering whether there was any point reporting all this to the PO, but in view of what you say, Munden and joban, I think I will.
BJ