What a god dam nightmare. I think I have finally got to the bottom of it.
After 3 1/2 hours of disconnecting and tracing wires, belling them out, testing for insulation resistance I found a fault on the near side front indicator circuit which when disconnected at the under bonnet multi plug seems to cure the faults. Further investigation revealed the self tapping screw holding the lamp unit into the housing was longer than it should have been and had punctured the lamp unit and had shorted it out internally.
Removing the self tapper cured all the faults.
All I have to do now is reassemble the car as it's in bits all over the garage.
A large whiskey and a rub down with a damp copy of The Bulletin I think is in order.
Thank you once again for all your advice, much appreciated.
