By the way after all the 3 plumbers visits and various expensive repair suggestions, I followed suggestion from Mike- Tech guy at Sentinel and put MX400 on 30/9/09. Within few days all RADs started getting hot and now I have also put the pump aon number 2 position and it is not pumping over anymore! I am now going to drain the system and put MX100 for protection So all those plumbers suggesting a Powerflush and plus repalcing the Hot water Cilinder were just trying on to rip me off. Total cost woul dhave been over £1600

How much this job should cost?

I have the same problem as metrolandman CH system. An engineer came and replaced the pump and then said I needed the power flush as my boiler was cutting off after2 to 3 minutes and no hot water or Heating. So I agreed and another engineer from the same company came to do power flush but told he cannot do it as I have old HW Cylinder and said that I needed to replace the cylinder at a cost of £950+Vat before he can do powerflush as it is old and may leak. I have a Potterton Profile 80e boiler and 12 RADS. It is an open vented system like yours. How was metrolandman problem sorted out? I have also been told on DIYnot forum that there may be blockage between the cold feed and vent! How do you clear the blockage?