Thanks Marty. Tested switch with finger from the underside of PF mate. Have removed the diode and wiring from the switch, and will re-wire either tonight or tomorrow. Bloody dinner (good thought it was) got finished then kids to bed, these things get in the way.
Diode seemed ok and continuity seemed ok. But never can tell, so thought I'd satisfy myself that wasn't the problem. Gonna work my way through....
Will keep you posted.