My boiler cutting out

This is clearly a boiler issue - it maybe electrics based external to the boiler pcb or within the pcb itself - this area of the boiler is not for any house owner to venture into and a registered Gas Safe Engineer or Company should be called upon. One simple test to perform would be to turn the boiler off on the front facia / dials then off at the switched fuse spare allow it five minutes and the switch the power back on at the switched fuse spare let the boiler register the power on then turn the dial on the facia back onto power the boiler allowing it to go through any start up process required ie using a reset button as described by the maker in the manufactures instructions for the house holder if not in possession of these then a search online will locate them

if you call a qualified gas engineer they should be able to asses the problem. use the gas safe register too find a local engineer