Going to get meter and test the wires as majority of earths are now clean and it hasn't made any difference but there could obviously be a break somewhere. Removed the headunit to see if this was causing any problems and this also made no difference so think I can rule that out too.

I need to source a wiring diagram as my workshop manual doesn’t have that in it. Dont suppose anybody has a .pdf they can e mail me in return for my eternal gratitude??