Hi Loulou - I've seen something on the forums here about this. It is a "freebie" but somtimes the garage forget and you have to ask for it. Someone posted a copy of the VW memo to VW garages somewhere on here. Don't forget to ask for it next Sunday - you could drive off without it in the excitment to hit the open road!
Yeah it is a special cable from VW. If the dealer doesn't know what he's looking for, he needs to check his desktop communication suite for memo 0510-08 issued on 14th August 2008. (Apparently anyway, can't claim the honours for getting the specific info, it was on another thread!)