I've been renting in London for the last 7 years, and in 7 different flats. Roughly half of those places had thermostats, and they were usually poorly placed. In all but one of the houses, the valves on the radiators had been removed (the handles at least), so it was pretty much impossible to control the temperature room-by-room. Have one flatmate who likes a cold room and another who likes a hot room? Tough luck.