Here's the step-by-step guide, it's really easy:

1. Purchase new loom

2. Run and connect following wires on new loom to the radio loom:
New Loom to Radio Loom (function, NavConnectorColour PinNumber)
Brown/black to Brown (ground, Blue pin10)
Red/green to Red/green (12V battery, Blue pin1)
White/grey/yellow to White/red/yellow (data bus, Blue pin3)
Violet/red to Violet/white (12V ignition, Violet pin3)
Yellow/red to Black/white (speed pulse, Violet pin 10)
Colours vary sometimes, but the primary colour is always the same.
Ask if unsure, or check to the actual pin numbers.

3. Run and connect wire on new loom to right-hand wheel arch wiring loom:
White/yellow to Blue/yellow (Reverse signal, Violet pin1)

4. Connect nav and of course the GPS antenna

5. Test and enjoy!


Of course, use all the usual safety measures when working on your car:
Disconnect battery
Unplug and remove modules / brackets etc to gain access to the wiring loom
Solder and insulate all wire joins. I used liquid vinyl insulation, easy to apply
especially in a confined space

To get to the right-rear whell arch you need to remove the rear seat squab. I run the reverse signal wire across the front of the rear set, under the carpet, where it won't get damaged. Easiest way.

You should be able to get the whole lot done in 1 or 2 hours, easily a Saturday afternoons work

For a GPS antenna, get a bog standard GPS antenna with an SMB connector on the end. I used a generic antenna, worked fine. Fit it under the parcel tray trim, in the same place as the factory antenna. Use double-sided tape to hold it in place. Run the GPS antenna cable down the side and through the wiring loom grommets, which are plainly visible when you have the seat squabs removed.