Glad it worked. I agree about the grounding concern, which is why I posted the schematic to show that the circuit is isolated and the 10V originates in the OE radio.Just confirming the wiring was bang on from JohnWR. Always dubious grounding a wire that says 10v on the description , however it was correct. Thanks to all, especially John. I now have to get the rear camera wiring through, but that's another day and then rebuild everything back up !
Camera wiring is not going to be fun. I have delayed doing mine for months. Maybe this spring.