As mentioned in an earlier post, I have (had) a W210 with a Nokia 3110 cradle. After hours of research, I thought I had the info I needed convert this for use with the Viseeo MBU 1000. At the last minute, I rang my local independant Mercedes repair place. By some miracle, he happened to have an old 6150 cradle (not UHI) and the right controller (part number A203 820 99 26, I think) in a box of bits. He connected it up for me and the Viseeo works perfectly (with a Samsung Tocco Lite - manual download of contacts neccessary). Well done Merc Medic near Guildford! I have the estate and the controller was in the back right next to the CD changer. The cradle is not fixed yet and I probably won't bother as it seems ok.
It just shows that it can be done, it is easy to do and the Viseeo works a treat. My thanks to all those here and elsewhere who have given so much helpful information.