Hot radiators when System turned off

[Sideshow]

Just had a new boiler fitted, along with new flow and return, new programmer for hot water and new motorised valves, system was working fine until this summer when decided to turn the system off.
When the hot water is used for a bath or out the sink the radiators start to heat up!!!!!

 

[ollski]

valve or valves?, because the problem you are having is usually a 3 way valve letting by.