Putting on hot water causes the heating to come on

[toby26]

I am quite inexperienced in this field.
We have got to the stage now where we have to turn all the radiators off if we want hot water, as even though the thermostat is turned down and the heating on our boiler has been turned off, the radiators still produce heat!
Our boiler is an ideal elan 2 from the Stelrad group and the heating / hot water control is honeywell.

Any help would be fantasstic!!!

 

[Boilerman2]

Heating Motorised Valve is letting by it will need to be replaced.

 

[toby26]

Thanks very much for the reply.
Whats the estimated cost for one of those?!

 

[combispecialist]

60 quid ish +labour