England's pretty safe. Obviously, there's gonna be some people, some younger teenagers or chavs, as we called it. I would bring some cash with you at all times, in case it ever is a need. But you don't have much to worry about really. I didn't really experience or hear of many crazy stories that were life-threatening anyway.
The heating over in England isn't like American heating and air conditioning isn't like that either. They use things called radiators which are just heaters on the walls. Don't get too close or else you'll burn yourself. And the air conditioning, well there really isn't any air conditioning because it doesn't get too hot, but if it does just open a window and that'll solve your problem honestly.