I spent some time in Northern Ireland and came away with two hundred NI pounds. Google claimed I could exchange them for BofE pounds at any bank. Stopped at a Lloyd’s Bank where I was told that without an account, they wouldn’t do the exchange and that probably no other bank would either. A few minutes later, on a whim, I stepped into a Natwest branch. “If there’s enough money in the top of the till, we’ll do it for you.” There was and they did. I was just a tourist off the street, and they were very kind. If I need a UK account in future, that’s where I’ll go.