my boiler had not been started for some time, it did however start up first time. It then cut out on F3 code (overheat). I realised that the pump had not been working, and I subsequently got this going. Since this time the boiler will not start, it goes through the start up process (fan operates and ignition spark operates) but boiler cuts out on code F1(no flame detected). Two fuses on PCB are ok and I dont know where to go next. Any help would be greatly received. Thanks