English, Scottish or Irish robbers. Have a great trip!

I can't think of any gestures or mannerisms which might offend or be misunderstood, as these don't tend to vary much between the US and the UK. As for things that you might say, if you happen to be taking a 'fanny pack' with you, please don't call it that over here. In British English, a 'fanny' is an intimate female body part, so ..that's an obvious one to avoid.

I was thinking more of any gestures, mannerisms, or sayings.

What sort of things did you have in mind?