I’ve never had any trouble with hotels in London. They’ve all been great. Well, maybe not the one I stayed in as a student in the late 70s. A cheap dump in Earl’s Court. But if you stay in a cheap dump in Earl’s Court, you get what you deserve.
My wife and I stayed five days at a Best Western on Belgravia Steet seven years ago. It was actually a refurbished flat or house and looked like one from the outside. Pretty decent but no air-conditioning. Since the temps at the time were in the 80s, it was pretty hot at night. Still a fairly nice experience.