On a prefacelift (as opposed to newer 147s with later firmware in the headunit), you should be able to add an auxiliary via the CD changer terminal. Off-the-shelf Blaupunkt aux adaptors don't work without minor modification to trick the headunit into thinking a CD changer is connected. There is info within these forums about it (I'd have to do the same search to find it, so will leave it to you).
There are occasionally ebay sellers who sell modified ones to suit the car, but I've not kept an eye out for them.
If you can't find the relevant info, shout out. From memory, these adaptors still only connect via the headphone output, and manually control the iPod. Not as good as a docking port adaptor (for sound quality), but you'll need to pay more for one of these; these usually allow control over the iPod via the headunit buttons too.