You could give this a go-
Another option is a Griffin iTrip system so you can either run an aux cable to it so as to run it directly through the radio and have remote control over your phone plus charging at the same time -
Of course you'll need the adaptor for the new type of connector on the iPhone 5-
I use an iTrip in my personal and work cars and it's ideal/works flawlessly.
Thanks, I had seen the USB thing but most info I can find states that it only works with mass storage devices (i.e. memory sticks) and not iPhones/iPods. Looks like if I was to replace the bluetooth unit for a later one then that might work though, but this is a pricier option.
I'd rather have something a bit more integrated than the iTrip, so the steering wheel controls etc still work, but thanks for the idea.