Don't know if this has already been suggested but a good tip to restoring marks and scratches on you BMW leather interior is to use boot polish.
I tried this on my 328i Convertible today, which has black leather, with amazing results, obviously you have to polish it well off afterwards.
Saves you a fortune as well against branded leather restorer. Morrisons price 39p for boot polish, branded leather restorer £???
Also don't bother with expensive leather cleaner either, use sainsburys leather wipes at a frction of the cost, the type you use on your leather suite at home, they work the same if not better and also have conditioner on them to protect your leather afterwards.