I had BG out due to problems with upstairs rads. 2 of them are cool at the bottom & warm at the top, and the other one has now stopped heating up altogether. Turned off all downstairs rads, put heating on full, but this does not make much difference. No air in rads. Pipes to these rads are plastic instead of copper (new extension - downstairs pipes all copper), & BG said that this was the problem as the pipes were unbarriered?? causing build-up of sludge. Said that barriered pipes should have been used, and have recommended a complete replacement of upstairs heating pipes at god only knows what cost. Are BG winding me up or not? Would some kind of flush solve the problem? Any advice gratefully received. (The upstairs extension was completed about 6 years ago).