Do you reckon it's definitely the pump, I tried turning the heating on today, it fired up automatically from the constant switch for bout 15 mins again, I opened 3 rads downstairs but the rad nearest the boiler was the only one with air in it, I went upstairs to the cylinder and the qualpex coming from the attic was throbbing with strong burses or water going through it, it was also very hot, can I not just turn off the power/water in the house before I change the pump, you were saying something about the 2 valves are these not the 2 3/4 inch pipes going in and out of the pump, one more thing, if I got a serviceman to come out he would obviously have to go and get a new pump before finishing the service which would be more money again because the grundfos pump isn't cheap thanks for this you've been so helpful Shane . .