Jay I think you are bob-on the money - you could quite easily put it down to being attracted to the Exotic, something that isn't the norm.

Trying to pick-up HBs we are obviously trying to stand-out from being social sheep in a positive way by offering fun and excitement.

If you are foreign, you are already different and exciting - you probably know another language, have your own racial look about you - there are tons of studies, particularly in China regarding why average foreign people are more attractive than avergae domestic people, and you can talk about your own culture which even between US and UK has some big differences.

I find it easier to pick-up foreign girls, as Knave said I've got a typical British accent, I'm average looking a toned and can hold good a conversation.