I will try to expand on the previous.
You need to in this order turn of your boiler electrically,isolate the flow and return iso valves,drain the boiler by opening the drain off small white valve behind condensate trap [bit awkward to access],while that drain is open attach a foot pump to the...
Batteries ?
Does the c.h light stay on on the boiler.If if goes of shortly after it comes on i would suggest your problem is the room stat/clock/wireless set up.You did not say if you could "link out " the controls or if you have checked any batteries.....These boilers are pretty good with...
It could be.......well many things....some more info would help How do you normally turn your heating on ? What type of "control" is it i.e a wired programmer a remote control room stat make model etc.You say your hot water is o.k so it follows that your boiler actually does fire.So all it...