If you want the Rolls-Royce iPod adapter you can go for the Dension ice>Link Gateway 500.
It lets you control the iPod from the stereo controls and seems to let you watch iPod videos on the car screen. I don't know anyone who has got one mind!
They are around £300 excluding fitting.
Isn't there an E90 compatible BMW OEM MOST iPod connector these days? I assume you don't have the USB connector.