Hmmm ok, I have pulled the unit out now. Had a look at a few forums the newer cars with the Bose system require the adapter. But I got lucky and found this site which has the same brand stereo I have just a slightly different model. I have the same 16pin connector!...

He has +12V constant power, ACC power labelled but not ground (earth)
There is a connector on the chassis of the unit which a thicker black wire with connector plugs onto (not the antenna connector which is round) am right to assume this is the ground (earth) connection?




You can see it clearly in this pic, it's that little metal spade piece on the left of the top white connector, that is where the thicker black wire connects to..