If get the wiring checked for breaks, in failing that is also recommend a diagnostic check to see if any fault codes flag up. Worse case scenario the CCM is on the way out
You could upgrade to Bose but you'd be better off just upgrading the head unit for a touch screen and aftermarket speakers. However I'm unsure whether it needs coding
The rarest part of the car is the colour. Besides that the 1.9tdi is still a common engine, but the 8l is now becoming rare. How many left is very inaccurate
Have you done a diagnostic check to see if any fault codes flag up with CCM?
Also have the carpets got wet at all? As a flooded CCM would often be the reason for it not to work.
Welcome to the forum you'll find the members on here are a friendly and helpful bunch.
Think you'll find the plastic backing is the back. Behind that there'll be foam, fabric and the frame