I had an A4 on hire with the Sat Nav disk in the front cd player..i removed it by ejecting it..but then put it back..coz im nice like that...honest guv'...The eject button is disabled by Audi at the factory. They say it is to prevent theft of the disk.
It can be unlocked either by your dealer or by someone with a VAG Com cable and software.
DoubleDoom is in your neck of the woods (Lowestoft) and will probably sort it out for you if you ask him nicely .
There are others mods that can be done - especially for the DRLs