Can I change a TRV thermostat head for another one?

I have a water filled radiator (part of my gas central heating system) which is not coming on.
I have worked out it is probably a faulty TRV thermostat valve, because when I unscrew the TRV head and leave it off, the radiator does get hot. (I have checked that the pin is loose and can move.)
Will a similar looking TRV valve head work, if I buy one and fit it? I'm wondering how standard they are. Obviously they are normally sold as a pair, the thermostat head and the valve itself.