The worst are the battery-operated thermostats that you install on individual radiators. Then inevitably the batteries will run empty and you will have a radiator heating full blast in the middle of summer...
Why would you have the heating on in the middle of the summer?
Radiator thermostats (TRVs) are for individual radiator control; they allow turning on/off zones when the heating is on, they don't control the heating itself.
It turns out that you don't even need those for the case where the radiator is difficult to access, because you can get an unpowered remote TRV that works via (it appears) some kind of heat pipe. Eg: https://www.screwfix.com/p/pegler-white-remote-adjustment-tr...
