Moving to London from Texas, will everyone stereotype me straight away?

Yes, you will get ribbed. And with all the animosity that GW has generated, some of it may not be in all good fun. However, keep your sense of humor. Brits are appreciative of good wit. My son did a study-abroad year at Leeds, and he was teased about stupid American tv shows, like Jerry Springer. He responded, "Nobody in America watches those. We just ship them overseas." When I was in the UK for business, I got the occasional, "Oh, you're an American." To which I would respond, "Worse - I'm a Texan."