Ah interesting. I saw these when dealing with the heated rear window not working(broken wires where the cables come thro' from the main body of the car). Not a nice job to do.
Do feedback how you get on.
Just to give you some feedback as requested, The hardest part was in general, removing the boot trim.
Once that was removed, the switch over of the unit was straight forward.
Once I followed the instructions and installed everything at the Radio end, it used all the exisiting OEM wiring, everything worked as it should.
Very happy with the kit.