Well I pulled the standard stereo apart but did'nt have any luck tracing the PCB and could'nt see any markings. But I did come accross these ready made mini wiring looms at Supercheap auto that enable you to just plug the new stereo into the existing plug.
So using that I just worked out where the wires went.
Pretty neat idea really - means absolutely no wire chopping when you want to upgrade your stereo!