hot water system works fine but no heating
pump works ok
thermostat is ok
when I put the 3-way valve into manual hot water is pumped around the system but in auto, nothing.
is this valve knackered.
Yes it is, if you have to move the vavle manually then it is deffo naffed. You can normally just buy the vavle head, the electric bit, on it's own try plumb centre there always good for things like this....