It started with some rads staying on when thermostat on wall and switch on boiler (not combi) was off, so had to switch the rads off manually. Was told it was the valve in the upstairs hall airing cupboard water tank, not working properly and letting the hot water go into radiators when central heating was off. He bought and fitted a new valve box, and didn't make any difference. Then rads started packing up altogether, some not heating up at all, weather it was on or off. I stopped water in small tank, and drained all rads out and bled them as two of them were leaking slightly at spindle on turn on and off valves, put new valves on, and put hot water on(not the heating) before I let the water back in, and got a dreadful drilling and banging noise in pipes and mainly coming from top airing cupboard where tank is. Turned it off quick, and was told that I shouldn't have switched hot water on until I had let water back in. I refilled rads, and tried hot water again, one loud noise, and then it stopped, then hot water working fine again, but now all the radiators are stone cold, do not come on at all when I put central heating on as well. Any ideas if it's the valve upstairs still, or have a done more damage to something else?