Bit of background:
We moved into a new house in Feb and when it got really cold, the heating wasn't really keeping the house warm enough. The radiators were really old and the OH's dad who is a retired plumber reckons they were a very old design that never radiated particularly well.
However, the heating was as near as damnit, silent. No clunks, bangs, whistles....
Recently we had all the radiators replaced (bar a couple), with new lockshield valves & TRV's on them too. We also had a new wireless Honeywell heating/hot water controller (Sundial RF Pack 2) and the guy who installed that noticed that the wiring to the motorised valve wasn't correct, which is why we had only been able to get hot water with the heating on (we'd been using the immersion for hot water over the summer - cheaper elec at night). He re-wired the valve correctly.
Now it's getting a bit colder & the heating is coming on more regularly, we are getting a steady banging through the pipes. It's quite well spaced out, about 10-20 secs generally, and seems to occur mainly when the system fires up. This means at the moment we are getting woken up at about 5:30 by this clanging noise and it's driving us mad.
I bled the radiators which helped, but hasn't cured it.
I tried opening the TRVs fully on the radiators closest to where the sound seemed to be coming from & this seemed to help for a day or two, but then it started again.
Last night we tried opening all the valves on all the TRVs to max, incase it was some kind of flow restriction issue (clutching at straws) but it was still banging this morning when it started up.
This evening I bled the radiators again and a bit more air came out of the bathroom rad (tallest upstairs radiator). COuld it be that there is air still making it's way round the system & once this is all out, the banging will stop? The system isn't really running for long periods at the moment, as it gets up to temp quickly, so I wondered if it just needed to run for an extended period to get the air shoved round to the bathroom rad?
I have also whacked the pump up from 2 to 3 (it's a grundfos with the 3-speed selector on it) and since then it seems to be banging less, but it does it worse from cold, so I won't really know if that's helped until 5:30 tomorrow morning....
Any things we can do/try? Advice? My next plan of attack was to check how open the lockshield valves are and see if there is one that's almost shut causing some kind of flow problem. I did wonder if this was the reason that the valve had been wired incorrectly - perhaps haivng the hot water/heating running in parallel cured the banging?
I keep meaning to ask my OH's dad about it, but he is quite busy at the moment and I haven't had the chance to pop round and quiz him.
don't say that! 
