Ultimately it will depend on what dealership (or stealership as I like to say) you go to. They all are mananged under different franchises (i.e. Cooper, Stirling etc).
I bought my BMW second hand from Cooper Reading stealer and I was pleased. They reduced the sticker price by around £700, gave me a full tank of fuel (however it was RON 95, NOT premium fuel like i requested), and changed air filter, 6 injectors and 3 coil packs and ofcourse a full valet before me collecting it.
I was also promised a BMW umbrella which I never got! Also i emailed them a few weeks later after I collected my car and told them I havn't got a torch in my e90 glove box. No reply!
However the car is in decent condition (otherwise I would have never bought) and it comes with a 1 year BMW warranty so I can't complain.