Central Heating Problem

[paddy07]

The hot water always works as programed but the only way the heating will come on is whilst the water is heating up. Once the water has reached the required temperature, the pump stops working and the radiators cool down.
I have had to switch the valve to manual position to allow the water to pump around. The radiators then continue to heat up then regardless of what temperature I have the wall thermostat set to? Does this mean that the valve is the issue? or could it be the thermostat?
Thanks

[gasman440]

problem is motorised valve ,motor needs changing

[paddy07]

Thanks for your answer gasman. In the end I managed to find that the white wire had come out from the valve. (the lead seems to be quiet short.)
However now the central heating comes on independantly but does not switch off when the temperature of the room stat is reached. We have had a new radiator put in in the bathroom in the summer and this has a TRV on. I can't remember if the previous one did, however all the radiators in the house now have one on. Do you think this coulde be causing the issue?
Thanks