Update - seems the main fan in the boiler has stopped turning. If I blow into the red pipe the pilot valve opens and the spark generator sparks - BUT the sp1 on the PCB sparks, none appear at the pilot light. If I manually light it the pilot lights but the main gas burner does not and as soon as the sparker stops sparking the pilot goes out. Obviously I will need a new fan but are there others issues here too?
Max p, March 2012