For starters dont be worried how people will take to you as an American, its so multi cultural here. People will most likely be interested in you I would think. I have someone come round to me and cut my hair, just a simple buzz cut/crop, shaved grade 2. It costs me £10 and I give her a pound tip. Considering she drives over, stops for coffee, and tidys up a little, I dont think that is a lot at all.