Tricky,
While you were fiddling around in the front of your car did you spot a little black lever to the side of the steering wheel? By moving this up or down you can use this to 'signal' the direction in which you intend to travel. I figure there must be a design flaw with BMWs as their drivers often seem to struggle to find this lever.
Only havin' a larf!
Me, I'm still struggling with my itrip!