Check the fuses for the BM54 radio module. Its in the boot, got at least 2 fuses, one in the fusebox, and another fitted to the module. Its next to the car battery buried deep in the boot.
That's assuming its not completely missing.
You can try rebooting the BM54 by unplugging the cables.. Again its next to the battery in the boot
After that you should get your radio/cd/tape and on board computer back again.
Any Sunroof on the car? Especially Panoramic, can leak water into the boot, causing all sorts of problems for the BM54 which is right in the bottom of the spare wheel well.
Check the fuse, try rebooting etc... If its broken there are plenty of people who repair them, and even upgrade them to include additional features and better sound quality.. They certainly can "crash" occasionally and unplugging them for a few minutes can often get it all back in order.