Eventually sorted !
Yes the harness was chaffed, on the LH side of the vehicle where it routes behind the heater/blower box and down the inside of the wing panels ( could only find it by pulling all the front LH harness out ). The short on the Green/Red had managed to burn through two earth cables and the headlamp feed. Lucky it didn't go up in flames ! Anyway a bit of deft soldering and the repair was okay. Why didn't they design the harness in "plug in" sections ?
However, still had a problem; which turned out to be the brand new "pattern" hazard warning switch that I had purchased. Detected the fault by following LandyMan Luke's technical guide and using a multimeter. Funny thing was that my existing switch would not work in the off position, whereas the new switch would not work in the on position. Thus I decided to strip down both switches and rebuild to make one working switch. Hey presto everything now works.
The only thing that now puzzles me, is the indicator relay ( not an OE Lucas ) it clicks like a metronome when I rev the engine; but works perfectly when I use the indicators or hazards.
Mmmmm, scratches one's chin !!!!!!!!!!!!!!