On the way back from the TVH Xmas lunch I noticed that the O/S front headlamp was very dim, the bulb was all ok so this meant there was an earth problem in the wiring loom.
Having taken off the nose cone grill and stainless steel side panel I found that the multi block on the Cortina loom was very corroded.
As the loom is so old now I just cut the multi block out of the loom and soldered in new joints and made up a good earth point on the body along with a new earth wire.
The loom now has Conduit Tube on it, this should keep any water out.