What type of Thermostat if any?

[RichardDIYPlumber]

I have a radiator in an upstairs bedroom. I fitted this myself some years ago and I didn’t attach a thermostat. The room now gets too hot when the central heating comes on. I’ve checked the fitting that connects to the radiator and I can’t fit the thermostat I have without draining down the central heating which I’m trying to avoid. I’ve uploaded some pictures. Does anyone know of anything that would be suitable to attach to this kind of fitting that could act as a thermostat or at least restrict the hot water going into the radiator so it doesn’t get as hot?

[marshian]

You could just shut the valve down to restrict the flow and manage the room temps 

 

Hot swapping rad valves without draining down can be done - but you need plenty of towels and everything near to hand

[Gone West]

Close the flow valve fully, counting the number of turns. Then open the valve half that number. Leave it a day and if the room temperature is still too hot, or not hot enough, adjust the valve accordingly.