Olly, it was one of the open (non trv-ed) rads which was my biggest problem. However, time and determination have fixed it. I have tried all the tips that have been given to me, and eventually i took a hose from the kitchen tap, connected it to the inlet pipe coming from the floor (rad was off wall by now) and flushed water down the pipe. Huge lump of rust flew out the drain valve outside, and voila! Radiator now heats very well!!!!
Pamela
February 2007