Help identifying TRV valves

[Yazza]

Evening all.
A couple of the TRV valves in my home have, over the past few months, had the plastic head come apart. I was hoping I could attach any TRV head, but that doesn't appear to be the case. The one I tried was equivalent to a very low setting, even when turned to max - the radiator was only luke warm.
The one in the hallway I'm not really bothered about as that is always set to max anyway (so that has the head completely removed), but the one in the bedroom I'd like to be able to set low (so that has the other brand of TRV to keep it on a minimum level).
If possible, could anyone identify the brand/model. I've looked over these with a magnifying glass but I can find no markings apart from numbers on the underside. Please see attached photos. Any help is much appreciated. Thanks

 

[45yearsagasman]

They look like Drayton heads to me.

 

[Yazza]

Does this mean any Drayton TRV would fit, or am I looking for a specific model? Thanks

 

[gasmanstu72]

They look like Drayton heads to me.

yeah, agreed.
the silver ring that holds them onto the valve is bust off

 

[gasmanstu72]

Does this mean any Drayton TRV would fit, or am I looking for a specific model? Thanks

try these, you could always take them back if they dont fit

http://www.screwfix.com/p/drayton-rt212-white-chrome-trv-15mm-angled/25900

 

[Yazza]

Thanks for that, I'll give it a shot.
Thanks for all your help guys, I wasn't expecting such a swift response.
Much appreciated.