too big that izzy, the others i have seen use one of these sony units,as they switch on and off with ignition.
http://www.ebay.co.uk/ctg/Sony-Nav-U-U92T-Sat-Nav-/110846516?_dmpt=UK_AudioTVElectronics_GPSSystems_GPSSystems&_pcategid=156955&_pcatid=121&_refkw=sony+nav+u&_trkparms=65%253A12%257C66%253A2%257C39%253A1%257C72%253A5788&_trksid=p3286.c0.m14
Was that meant to be a link for Sony head unit or a standard Sony sat nav? Showed a link to a standard sat nav??