Rayburn hot water working but no central heating

[Abracadabra]

We have an oil fired rayburn 880k regularly serviced. The hot water and cooker are working fine but the central heating is not coming on. The cooker is on manual at the moment 24/7, not on the timer but it does work fine on the timer. We have replaced the room thermostat in case it was that. The thermostat clicks to call for the heating but the boiler does not start up. Wr have a pressurised system and recently have been added i believe to an overhead water tower that feeds the village, I think until then we were on a mains pipe, could this be an issue? We have checked the pressure on the dial and this seems ok, also there are 2 valves and they both move so presume they are ok. Any thoughts on what the solution could be?

 

[oilhead]

Check the electric supply from the programmer, then from the priority switch on the Rayburn, then the operation of the microswitch in the control valve, presume nothing, just check.
The water supply will have no effect on your problem.

 

[Terrywookfit]

The water main is fed from the tower.

 

[Abracadabra]

Thanks for replying, we called an electrician out to check the programmer, he pressed the boost button on it for the heating and the boiler typically started up i couldnt believe it. Anyway he said if it happened again we would need a new programmer, we have a horsmann multi programmer channel 1 for cooker2 for heating 3 for water, 1and 3 working fine. The next day, heating not coming on again even after doing factory reset and trying the boost. Re programmed the whole thing evening and guess what the heating has been on again. So will see what happens tomorrow but guess it must be the programmer with an intermittent fault?