been to the caravan again today armed with screwdrivers and tester.
all fuses are good, so no probs there....checked inside the zig unit and cant see anything visably wrong, so i poped the tester to find the dead wiring, it was on the middle of the connection block, so swapped them with an outlet on the wiring block that read live, hey presto the green light came on on the heater control pannel...so its looking like a fried zig,
asked at a local caravan breakers and they didnt have one but hes hoping to get one in soon...