It's perfectly ok to be addressed as "love" by another man, but only in Yorkshire; don't return the greeting in kind, though, unless you have a local accent. Other things to watch out for:

"Fags" are cigarettes. "Faggots" are a kind of small, skinless haggis (but with a lower cereal content, and often served in gravy). "Biscuits" are what Americans call crackers; or, if sweet, cookies. So far as I can remember, American "biscuit" is more like what we'd call Yorkshire Pudding, though of the dense rather that risen variety.

If you need to buy an eraser, try to keep a straight face and ask for a rubber. It will be easier in the long run.

Never talk about "pants" except as a joke. Be very careful how, and to whom, you use the word "fanny".

You probably know all that already, but it's amusing to mention it anyway. On the whole, I'd say make the most of being a wee bit foreign; people rather like it as long as you don't mind queueing and never say things like "you Brits", or imply that things are better back home (even if they are). Most people quite like Americans (most of us have family there), but we do moan about them, on a generic sort of basis; don't take it personally.

Things like Marmite and proper beer are only appreciated with practice; be patient if you haven't already had the groundwork in that. It will come. We have a better selection of bread than we used to, but do buy the more expensive orange juice in order to avoid too much culture-shock.