normanh, I assume the car is an E90? If so it is not a good deal in my view. You can get a brand new E90 330d M Sport Auto with Lthr, Pro Nav, Bi-Xenons for less than £32000 (drivethedeal.com) you would also qualify for cheaper BMW finance so it probably works out cheaper all round IMHO.
At £28K and over 1 year old, that car is overpriced by a couple of grand at least. If you fancy it go in hard and get some money taken off. I'd go for the one with SatNav, privacy glass can be retro-fitted quite easily I think.