Steering Wheel controls in a VT series 2 Exec??

[-=$natch=-]

Hey guys, I fitted a head unit & stacker from a VT Calais into a mates series 2 VX Exec wagon and I noticed that it only has one plug and has a couple of different wires. It already has the steering wheel controls, but I'm guessing that I have to alter a couple of wires to get the steering wheel controls working? I think there's only 2 that have to be changed? Something about the wires going via the bcm instead of directly to the headunit, so i have to chop these wires and put them straight into the back of the headunit is that right? Any help, including a wiring diagram would be much appreciated.

Thanks

 

[-=$natch=-]

Does anyone have a wiring diagram that they can scan, at least with that I should be able to suss it out??