To be honest, after recently driving an E60 BMW 530D I would have gone for one of those for that sort of money. £20k would have bought you an absolute minter.
Example:
http://pictures.autotrader.co.uk/ATD_web/servlet/media?id=598366189
That is a 530d Sport. £20k will NOT buy you an absolute minter of an E60 530d Sport. It will barely by you a thrashed potting shed of a 530d Sport.