I'm trying to connect my Sony CDX-GT30Rn to my 2004 Vectra (with the older style steering controls and the large screen trip computer)

With a bog standard ISO lead it works fine, but I would like to use the steering controls and screen if possible. Now, this Sony unit was in my old Renault Megane and has a mini-iso socket where the Renault yellow mini iso connector went, which made the Meganes steering controls and screen work with the unit.

Is there any way to do this? Or if someone can tell me the pin arrangement on the Vectra I can maybe buy blank mini-iso connectors and make my own up? The Sony unit was obviously made with CANBus in mind as the instructions refer to it but only relating to Renaults!