ok...
So I tested the wiring that plugs into the temp/fuel gauge and there is power there. I Upgraded the old thermal voltage regulator to a solid state regulator which fixes the issue of the old one frying... ( link here>>> http://holdenpaedia.oldholden.com/Fuel_Gauge ).
This has fixed the issue of no back light illumination, but there is still no movement in the gauges.
So... Sounds like an issue with the sender now? Is there a wire that leads from the sender that could be disconnected anywhere?
Thanks guys.