the thermostatic controller has snapped off the top of one of the radiator valves is the threaded metal collar standard to all valves?
Can I fit one fro a different make?
Not (AFAIK) interchangeable between manufacturers but there are a relatively small number of common makes. Can you upload a photo of the one you're trying to replace?
Buy one to try. If it's what you want and they're only £6 a pop, I'd recommend you buy a replacement for all of the ones you've got of the same age as the one that's failed because you'll probably find they are all about fail in the same way.
You've been very, very lucky. Looked familiar (as they all do) but couldn't ID, it was the first one that popped up on an image search and they sell the heads seperately too which is unusual for a non brand.