Whitespirit66 - thanks for taking the time reply :D
*shivers in the cold spare room*
In the meantime would there be any issue with me removing the head? When I did this the radiator heated up. Obviously I won't be able to temperature control the room but as the thermostat is located...
Last night I discovered my bedroom radiator was cold, and having taken the TRV off found that it was the issue. I then swapped it with a working TRV from my spare room. The make of them is Caleffi.
I am now wondering whether the TRV caphead bit is broken beyond repair.
In the middle of...