Replied in other thread as well but...
When i bought my 330d Sport, general consensus on forums was you dont get much more MPG from a 320, takling a few mpg.
Plus the 6 cylinder is worth it for its smothness.
RE tax, hardly call it a lot, 210 for the year (maybe less on a newer model)thats group K i think, regardless, thats less than i paid for my older cars, ie 205 gti, Crx vtec etc. Even though Crx was a 1.6!
Insurance shouldnt be bad unless your young, I pay 550 fully comp, clean license, no accidents etc. 10 yrs NCB, im 29. Same as i paid Flux for my engine swapped, extremely modded 205, and same as my Import Crx Vtec B16.
I will say though, Flux wanted like £1k for some crazy reason. So ended up on good old meerkat.
They dont feel 'fast', there heavy cars, but the power is smooth and constant. Unlike some cars, where the delivery is more abrupt once the turbo spools up. Its no slouch though. Mines a manual, i dont touch autos.
I get 45-47 mpg driving sensibly. On a mix of town and motorway. Will see low 50s on a long run, and low 40s if short journeys.