Just to update this and yes I know it’s been a while but life just gets in the way sometimes.
Tested headlights and had no hi or low beams, no relays clicking, nothing! So tank and air box etc off. Took the yellow connector apart, a little bit of corrosion but cleaned up OK with some contact cleaner. Then the lights worked again putting the air box back on the lights cut out again.
So air box back off again, wiggled the yellow plug and the lights came back on again.
So you clever blokes were spot on with it being the yellow plug. Pulled a couple of the pins out and more corrosion and a couple of connectors just about hanging on to the wires.
I’m going to cut out the connector and fit a new one