could be the radiator is full of gunk? if its a little bit warm this is most likely the case,try turning all ur radiators off except the one in the bedroom and leave it for about 15mins and if you get heat then balance all the rads out until there all banging heat out.if not it sounds like the trv has failed just replace the trv(and give the radiator a flush out while its off) they dont cost that much.if that doesnt solve it,it could be something to do with the flow supply
plumber grant, December 2009