Thorn 80/100C Boiler-how do I get it to work???

This gas boiler has always worked well. The pilot light is on, and it is connected to a mains electrical supply (and a timer/heating selector). The electricity supply to the house failed (the main RCB cut out and it took several attempts to reset) and has now been restored, but the boiler will not fire up. The timer/heating selector is not keeping time-it appears not to be working, but I have checked the cable and the fuse/supply is ok. I have pressed the bitton selector for continuous (as opposed to a timed input), but nothing happens (that is, the boiler does not fire). Any help gratefully received. This has never happened before.