I've just moved house, and the bloke did mention when I was looking round that the upstairs rads sometimes dont get warm, but you just have to shut in the small rad in the hall and they heat up. It didnt really phase me, because I really liked the house. Now i've moved in, the rads upstairs didnt get warm at all, so I balanced the system, got 1 rad out of 3 working. I really gagged in quite a few of the rads downstairs and managed to get 2 out of the 3 upstairs radiators heating up. I have almost no experience with system boiler setups, but getting my head around the system it looks like its a case of the boiler (obviously), which feeds a pump, then into a 3 way mid position valve (or whatever it is called). The CH side then just goes through the floor and off to the rads, the HW side goes into a tank with an expansion header. Obviously this could be caused by a number of issues, but ive bled and balanced the system, and the only way I can get the upstairs rads to heat up is by gagging in quite a few radiators. Can I just uprate this pump, does this sound like it would solve the issue. Personally I think there are far too many rads in the house.
Appologies for the story,