Potterton Netaheat 16/22 Boiler - No pilot light?

this boiler recently stopped lighting up - i spoke to a freind plumber over phone and he said it could be the pcb board and the valve switch is stiuc - i was advised to tap that area and see what happens - the fan is on but no flames - whilst hovering the dust and webs away i touched one of the cables - not sure which but under the igniter genearator and then the boiler fired up - now when i ned to start it i have to hit it and then there is a spark and he presto - i have been told it could bethe air pressure switch as the fan is on - thinking of cleaning the rubber pipes to this - anything else i should try and if need new pressure swithch where can i get it the part number is 64220403 but baxi tell me it is an obsolete item - any help appreciated. thanks