wiring for steering wheel controls astra mk4

[rgv_stu]

right then does anyone have an astra mk4 wiring diagram anywhere? specifically the wiring from steering wheel controls to headunit and whatever in between.

im looking to use the steering wheel controls on my mk4 astra with a sony headunit

where abouts do the wires for the steering wheel controls go to? do they go direct to the CAR400 headunit or do they go to the multi function display ? or somewhere else ??
how many cores to the cable?

i know i can buy an adapter but i have made one in the past for my sony for some custom switches on my old nova, i wanna do the same if i can using the astra switches.

[rgv_stu]

or has anyone got one of the auto lead converters and opened it up?? there cant be much to it as the sony remotes only switch an inline resistor...

[cavbow]

bought a autolead 1 for my Zafira didn't cost to much about £14 if i remember