It would be great to find someone that could repair these in your own country, however, all the links listed for repair places do not repair these units.
If you have a look at them, its mainly simple stuff like, fixing tape players, cd players and very old units.
Here is an example of lack of knowledge, from one of these sites. It quotes
If you have Blank screen with or without lines and audio cuts out after 3 minutes, then your navigation unit in your trunk is defetive.
It is referring to the navigation drives in the bmw cars. Which consists of a screen, that acts like a dummy, powered by navigation unit and radio module. So saying that the navi unit is at fault for the sound is incredibly stupid. Never heard such nonsense before. If they dont even know where the sound comes from, then they are obviously clueless. And it does give you a quote for a price on a whole new board replacement, which is what they probably do.
Most of the repair companies probably outsource the repairs, and since becker has stopped providing support for these units, i doubt they can help anyone any more.
That is just my view, of what I have read from this thread and the links provided.
If you do send your unit to these companies, make sure its a no repair no cost policy.
I have just finished developing a smaller kit, which will let you keep the cd player. You can still have the AUX in option. I have also finished, developing a bluetooth feature, which lets you stream music directly from your phone.