Cheers.

I have the headunit working. Steering controls do not work, but that is a minor inconvenience.
I tapped into the Glove Box Torch (Purple wire) for the Switched Live.

Main pain is that the headunits wiring came with 2 iso connectors. Which I cannot use due to the X5 having a wide screen satnav and DSP.
This makes wiring difficult for an amateur like me.

Questions:
For the Illumination, Could I tap into the X18801 (Blue Connector):
Pos 1 - Night light signal Connector?
So when I turn the headlights on, the Headunits buttons should illuminate.
This will connect to the Orange wire going to the H/U.

There are many wires which go from the H/U into a small module titled "CAN BUS Decoder". Unsure what to do with most of these.
The wires are:
Red - Switched Live
White
Green
Orange with white stripe (splits off into a wire to H/U and a wire called BACK-CAR)
Yellow - Permanent Live
Orange (loops into 2x iso connectors)
Pink (splits off into a wire to H/U and a wire called BRAKE CTRL)
Orange (splits into a wire to H/U and a wire called ILL)
Black - Ground

There is also a Yellow RCA type connector called CCD AVIN which cones off the H/U connector. I am assuming this is for a Reversing Camera?
How would the H/U know the Reverse is engaged in order to flip the images being displayed on the screen to that of the Reverse camera?
The Reverse camera I have has the following:
Yellow RCA on the camera module - for Video
Positive power wire - I can tap into the Rear reverse light wiring harness for this
Negative power wire - I can tap into the Rear reverse light wiring harness for this
It then has a long Yellow RCA cable, assuming this is to route to the H/U.
On both sides of this Yellow RCA cable, there is a Red wire. I am assuming this is for a signal to tell the H/U reverse has been engaged? If so, where would the H/U side's Red Wire connect into? Maybe it connects to Pos 6, Blue wire, CAM-LINE in my picture (Blue Box, Section K)


There is a Brown wire called KEY1. I think this is for the steering wheel controls, but cannot be sure. What would I connect this to?
According to the Picture I posted, there are 2 KEYS, K1 (Pos 3, Brown) and K2 (Pos 12, Brown+White). Surely both should be connected?

Sorry, More Questions:
In the Green Box in my picture (H connector), there are 2 Yellow RCA connectors.
Pos 5, Video IN - Assuming this will play anything so long as source is transmitting via Composite out? (Sound will be via the Aux R and Aux L)

Pos 6, DVR-CVBS - Unsure what this is. I am assuming it is the same as VIDEO IN, however this is purely for video, so no sound via Aux R and Aux L?

Pos 3, TV-IR - This seems to be a standard wire with a clear/blueish plastic cap over it. What would this be for? IR suggests infrared?