Central heating now working ok after a I eventually told the heating engineer that I thought the problem was the diverter valve ( after advise from people on this forum) so he replaced it, this whole episode has cost me a total of £697 £180 for the replacement pump ( experts origonal diagnosis) £300 for power flush ( another experts diagnosis ) £217 for replacement diverter valve and yet another pump, apparently the way the boiler was recirculating straight through the boiler damaged the pump ??? and we are all advised not to do it ourselves (by experts) anyway thanks for all your help. By the way does anybody out there know where I can buy just the wax module for this Potterton combi 80 (Puma) diverter valve ? so I can recon the origonal valve ready for the next time.