High 30's MPG on a near 300bhp car, tonnes of torque and coming in at decent mileage sub £18k is a pure win IMO, but I would be biased! 330D manual would be my next option but I'm a D wh*re through and through.
Yes they might be more costlier upfront but man do they pull! Having come from a 320D and driving in a 520D recently just makes me appreciate my 335D to another level. I get up early to have a bit of a longer drive sometimes just to enjoy her!
Do what's best but don't be afraid of mileage on a 335D. On motorwary you'll get 40+ and mixed driving, mid to high 30's. After a remap, even more! Even the LCI 325D is worth a short but if it were me, 330D or 335D if the price warrantied! Happy shopping :-)
Now: E92 335D
Gone But Not Forgotten: E90 320D Alpine White