Well, I've started and it has not gone well! - thought I'd test the head unit first. Plugged everything up, attached the connects2 harness and patch cable for aux input, plus antenna etc. Radio/stereo seems to work fine, but the steering wheel controls and aux-in don't work. I'm suspecting that it's to do with the harness adapter as, the SEAT plug has some blue socket at the corner of the big connector, whereas the Connects2 plug doesn't have any pins for this (see pic) or could it be something else?