A 320d will be cheaper both in terms of lower BIK and yes better fuel economy
We don't know the real world economy of the new 330d. I imagine a large part of the increase in mpg stats is stop/start being introduced.
My efficient dynamics 330d can get 47- 50mpg in a run if I take it real steady and gentle, overall it gets about 39mpg. If you go in town or touch the loud pedal it's a lot less
