To be honest, a diesel BX is hardly the best diesel in the world! As you know, nor is the DCi 2.2. Most modern diesels are superb, I get along with them very well for the low down torque, economy and excellent refinement - the most important thing to me. Why spend more on fuel than you have to, especially if your not even getting increased performance or a nice sound (anthing less than a turbo petrol or V6 and above im meaning).
I think you should get a 2.0 HDi 138 Peugeot 407 in purple with leather and enjoy the 50mpg average and excellent engine and box
You should be impressed with it, I like mine. I know you will probably never be converted to diesels but if it was a diesel BX which put you off, you should really try some better and more refined diesels.
What, apart from this BX, do you think might be your next Citroen?