Maybe you could try draining water out of the upstairs radiators, grab a radiator key and on top of the radiator there should be a slot for the key turn it but have a container ready to catch the water, do this while the CH is on, you should hear a hissing sound meaning there is no more air in the radiator. When the hissing is gone turn t6he key back, your radiators should get hot, but if they still don't then there's another fault with it and you should get it seen by a CORGI registered workman. Hope that helps.
Anonymous, January 2008