Hi Matt
It's a strange thing with these headunits, well sony ones.
Those aux inputs are designed for the CD changer input and the unit needs to be fooled into electrically activating the ports.
I have found an adaptor on ebay that does the job just fine!
I spent ages hunting down why i couldn't get it to work and just stumbled accross this little box!
It does mean spending a few quid but i suppose its cheaper than a new head unit.
Hope this helps
Andy, January 2008