Tipping does not exist in the UK for some reason
It does, but we generally resent it and it's not common to all places.
It pretty much only happens in restaurants.
10% is the UK average/norm, although the English apparently tip 8% on average while Welsh tip over 10%.
I would only tip in a restaurant, and usually just the change from my pay. Maybe a more specific tip if a waiter has been really good.
But we generally don't need to tip because we have a national minimum wage for all jobs. A full time waitress may earn no more than a full time shop assistant, and we don't tip those.
I've never heard of tipping barbers/hairdressers either.