1 cold rad

I know there's several people on here with the same sort of problem but...
We have 1 radiator (of 11 in the house) which has stopped heating up. Ive tried bleeding which has done nothing, so tried leaving the valve open for a litle longer whilst the water comes out of the valve, thinking that there is some sort of air block in the rad. This actually caused the rad to start to heat up, but after taking two buckets of water out I thought i better stop! Ive obviously topped up the water in the system after the draining. Only the inlet pipe is hot, with the outlet being stone cold, and it has a thermostatic valve fitted which i havent tried removing, yet...

Try taking white part of trv off spray valve with wd40 press small brass valve up down with screwdriver see if this loosens the valve.

do you mean the thermostatic valve?? & if i start taking this off is it likely to all of a sudden fall apart so i cant put it back together again??!

I suppose the hot pipe is on the trv end(the thermostatic valve) depending on which make the valve should be easy to take off open it fully there should be a plastic fitting under the valve should turn off with your hand or use small grips to crack it open this will leave u with the valve to spray wd40 onto and no water will not go everywhere.

ok, firstly the valve is at the other end of the rad - ie the hot water comes in from the other end. But the only way i managed to get hot water into the rad was by letting the water out of the rad through the bleeding valve. This makes it sound like, to me, that it is a problem with the thermostatic valve?
Anyway, i managed to take the whole valve off, and i'm left with two brass bolts, one smaller one on top of a slightly larger one, then coming out of the top of the smaller bolt is a little pin. Now I checked another rad in the house and the pin on this one was a lot higher than on the one which isntg working. & I had a look inside the thermo valve & i just cant see how it turns the rad on or off & this too has a plastic bolt inside it, as i though it would have had an inset for the brass bolt to sit in? Or is this not how the rads work??