I would have said 12-13k, and 12k sounds good as a PX figure IMHO. Your car has the important 6 cylinder car options ie auto, leather and nav.
Some jokers at Bowker Preston told me recently that my car (2010 individual, every option possible except folding mirrors, dab and tv) books at 14.5k (!) and that was against a not-exactly-easy-to-shift 550i at £40k
Current: F10 550i
Previous: E61 550i, E90 335i, E87 130i, E87 118d, Z4M, Z4 3.0i SMG, E46 330D, Z3M, Z3 3.0i, Z3 3.0i (US)