boiler gives hot water,but no heating,runs of a rc ,plus wireless timer and reciever box ,not sure if one is broke,replaced batteries in thermostat,turned of at mains,then replaced batteries again,still nothing,timer comes on flame calls for heat green light on receiver comes but does not switch the boiler on,no other form of heating,any ideas would be grately appreciated,and have tried manual override no look,as its as cold inside as out with all this snow,thanks