My next car will be either the 320d or 330d, so i dont blame you one bit! Note the manual is far better on mpg.
I don't agree with this talk of diesels being more expensive if you don't do plus average miles either, unless you're talking about cost of buying a car brand new - then it might be different.
I get between 550 and 600 miles per tank out of my golf, and you can still give it beans. To keep up in a bigger cc petrol or simlar capacity turbo'd car you'd dent your mpg significantly, and probably get no more than 300 - 350 to the equivalent tank!?!
dpf removal and remap = big gains too
Tom