If I go into a bank from my own country, can I change my money to a different currency without a bank account?

So, if I go into a bank (in England), without a bank account for that bank, can I exchange, for example, 5 GBP to the equivalent of a different country's currency (like dollars - USD - or euros)? Cause I want to change some of my money into dollars, but I don't have a bank account for any bank.