Headlight problems

[Motorway]

Hi, new to the forum so please go easy!
I’ve just acquired 2x 1984 GTX. One is a doner and one I hope to fix up after being stood for 10 years.
The car runs perfectly and everything appears to work bar the horn and headlights (I have the sidelights)
I can’t get main, dip or flash to work and the blue light doesn’t illuminate.
I have cleaned and checked the earth crowns and all the fuse box connections. Cleaned and checked the main battery earth at both ends and the rocker cover to bulkhead earth. The switch supplies 12v to the stalk ok (black and white). I’ve removed the stalk and tried to bridge the power (yellow/red) to the main (white) and dip (yellow) circuits with no joy. New bulbs fitted.
So now I’m stumped. Any help would be appreciated and sorry for my long, first post. Thanks Mark.