Hi.
I have now connected my steering wheel up and configured the controls.
It is straight forward and should work first time.
The connections from the steering wheel are on two thin wires Blue & Blue with orange tracer.
These will need to be cut from the loom and one fed to the Power ISO connector on the set and the other one of them to earth. I used another ISO connector and salvaged one lead and internal connector and fed it into my existing ISO plug.
It makes no difference which lead you earth or connect to the radio as the wheel controls only select different resistors on each function.
Once complete go to settings and then wheel controls do each one at a time, EG go to Vol + and press Vol + on the wheel and a tick will appear next to it on the display, once done press OK.
Job done.
The last two pictures show the steering wheel cables from a Hi-Line loom, On the BMW connector they can be found easily enough, also the ISO plug supplied with the radio, its the Orange & Black tracer lead on pin 3.
WARNING: There is a 3.5mm jack socket on the rear of these units which has a constant 5v on the innermost connection. Under no circumstances use this as an input, possible damage may be done to the connected device.