Hey Jack, I just look at the turn signal box and there is no wiring diagram. It only comes with a parts list and some instructions.
Call ARB tech center and they will help you out. They are pretty good at it.
The rack on the Defender is definitely an ARB but it is not my Defender. I own a Classic two door Range Rover. I just pulled that pic from the web.
I had several inquiries about the side rails on the Defender and again it is not mine. I checked my export ARB catalog and apparently they are not longer offered. I only found some for Toyotas.
Good luck!