I have 2 rads in dining room and hallway which are not working, both have thermostatic valves. One of the radiators is warm up to the thermostatic valve but the rad is only warm at the top and the return pipework is cold, the other rad both feed and return pipe work is cold. Both are fed from upstairs and some of the pipe work is visable one pipe is hot and the other cold. I have tried tapping the pins on the valves thinking they are blocked but no change. Have read of the same kind of problem on this site and balancing has been mentioned can anyone enlighten me please.