Hi
If anyone is interested in upgrade to BT there is some information about parts. I have 2004 x5 with S640A (pre-wired).
I had to buy and install:

1. ULF module #84 21 6 945 387 or latest
2. microphone #84 31 6 938 762
3. bluetooth antenna #84 50 8 387 422
4. cable between ULF and antenna #61 12 0 137 616
5. eject box #84 21 6 933 413(415)

That's all.
Maybe it'll be helpfull