I don't think so? hate to give a dull answer, but it just seems kind of normal after about 5 minutes. Unless you visit the North or (shudder) North [i]Wales[/i]- in which case it's basically like listening to a foreign language anyway.

Generally? The american's I've known in England have loved it, more cause of the strange culture differences than the accents. It's not like living in a BBC period drama (apart from Wales and the North which are basically the nasty bits of Dickens), sadly.