People often used to accuse me of being Scottish or Welsh at uni. I got asked if I was American, Canadian, Australian and a few others too.
My sister works in a call centre and at least a couple of times a day she gets 'accused' of being Welsh or Scottish - most frequently Welsh. Apparently some people get quite angry with her and accuse her of lying when she says she is actually a Geordie! Could be worse - they could accuse her of being a Smoggy or a Maccum.