Well, I would say that Heathrow is fine. I also used to work in Air traffic and I know the excellent standard of ATC in this country.
I would say the toughest airfields are the Channel Islands with the strong winds. But, I would say the worst for near misses is White Waltham. I have nearly come a croppppper in there many a time with the amount of aircraft and lack of ATC and aircraft without a radio. It’s madness on a nice Sunday afternoon.