exchange GBP in Iran – Travel Stack Exchange

GBP is amongst most popular foreign currencies in Iran and I believe you will be able to exchange it easily.

I have no experience with exchanging GBP myself, however, I had no problem in exchanging 100,200ies of Euro (in Rasht, a rather small city in the Northern Iran); 50 GBP (or even bigger notes) should be fine! ( but anyway you should get used to carrying too much paper, as eventually in Iran you will! )