I came here to report the same problem, and found this topic. I have an xperia 10 single sim running 3.3.0.16, and my car is also a VW with factory bluetooth. Handsfree profile connecting seems to be random. Sometimes it connects and I see battery and signal level and mobile network name in the car instrument cluster, but the majority of the time it just shows the phone name and I cant access the address book or answer/make calls. Audio streaming works fine. Pairing and unpairing seems to make no difference. Specifying HFP on the phone does not help. I thought once that it started working after I enabled mobile data (which i dont know why it was disabled) but actually there was no causation here as it is still random afterwards.
Would love to get this working as I really need calls to work. I will try the 3.4 update to see if it helps but if not I will have to use an android phone until it’s working again as I use the phone in the car a lot!