Already checked the pin. Both valves were fitted as per instructions. You can feel just past the TRV and its piping hot but it just doesnt seem to move further into the radiator, if that makes sense.
Drain the radiator, and check you have a flow through it with a hose pipe.
While you have it off, open the TRV so see if you have a flow through it.
How are you opening the lockshield valve, did you remove the cap and turn the spindle.