I am a native English speaker, although American English, not British English. Anyhow, this is an interesting question to pose to ESL students out there. I can't think of any off the top of my head that would pose a problem with pronunciation but some interesting American English (or at least I do not know if they are part of British English vocabulary now too) that people might want to check out are "power nap", "staycation", "selfie", "twerk", etc. :)