The sat nav must have the eject button disabled, forget what the technical name is, basically it stops people pinching the disk in loan cars etc. You need someone with vagcom or nip to the dealers and get it put on default ie the eject button working.
Coding is
Channel 067 (Eject CD/DVD)
000 - default
001 - eject CD/DVD
255 - eject button locked, no eject possible