OK ... THIS IS SERIOUSLY STARTING TO GET ON MY T*TS!!! Is there an easy way to identify a circuit diagram of the plumbing, from the pump onwards ... i.e. to which rads, whether its a single feed/return or dual, etc. as some rads work, some don't at all, some are lukewarm after 2hrs of running. The boiler pops every now and then, and I've bled it sill, so it surely must be flow restriction, causing the boiler to self-check and overheat, thus it popping, and perhaps explaining why some rads work and some don't. The downstairs rads - there's only two - one's mediocre the other's lukewarm at best. It all used to work okay a while back, then the bathroom rad stopped working and I assumed it was one or both of the valves. When I checked today (after flushing) it turns out the valves are okay. Now its fitted on a laminate floor - i.e. right ol' mess and hoo haah to remove and check pipe under the floor, but I'm sure I recall when the floor was up that it was the same pipe going past both valves with Ts in. Please, I beg, on bended knee, at risk of doing a whole crate of wife basher if I don't get even a small win today ... I've spent tons just before crimbo on stuff that's made little or no difference ... AARRGGHH