Any diesel before Euro 6 (mandated from around Sept 2015, iirc, but some BMW diesels were EU6 compliant earlier - back to F10 530d around the LCI in 2013 being the earliest example I think (or 330d/730d, etc. with Blue-Performance option specified from around 2012) will be fleeced for NOx, so well worth thinking about a petrol as an alternative. In the case of the e60 535d, the CO2 category/rate is the same for a 530i (LCI - N53), with similar power, etc, but NOx on the petrol is a small fraction, so there's a big difference in the on-the-road cost of an import (still a ridiculous final number). It makes it worth considering the real delta cost to running a petrol and how long the extra running costs would be covered by the difference.

Alternatively, if you must go diesel, its worth thinking whether something EU6 compliant and a few years newer may only be marginally more expensive to get on-the-road, e.g. an LCI 530d, or Blue-Performance specified car (535d wasn't EU6 compliant until later, maybe early in 2015, would need to dig a little to remind and confirm the precise timing).