That's pretty high for a 320i, even automatic I would think - depends on how it is driven and what type of driving we are talking about. Both my car and my Wife's 320i CAN be very heavy on fuel or fairly light - short frequent trips from cold eats fuel in particular with mine, so once up to temperature and at decent speeds she sips very nicely. The econometer on both cars react almost the same under the same conditions although where mine differs from the 320i is that mine take a lot more convincing to come down and below the 10 l/100 km instant consumption in traffic and so on!
Is automatic a must? Just by opting for a manual car can save a little on fuel usage, but still many factors can change this. By no means am I against the 1 Series - was actually very seriously considering spending a bit more and getting a 120i with lower mileage for my Wife. But my original plan was to get her a nice E46 with a manual 6I in particular, and glad I did so.
So some things to thing about, rather the "devil" you know - so much knowledge and DIY solutions for E46's, especially here, but these cars are somewhat predictable. Known problems are well documented and in most cases easily fixed. Then with the 1 Series you have the whole RFT's and no spare wheel for your Wife to battle with. Some complain about very heavy steering and quite harsh rides in some cases - this is also down to personal taste. Even my E90's steering is a tad heavier that the E46 - get into my Isuzu DC and have to consciously remind myself that I am now working with super-light steering even though we are in HMS Isuzu, and try no to bliksem the thing onto its side while turning... At the end I think, if you get anything from a 116i to a 120i with a manual gearbox, or even an E46 with a manual gearbox you will already have less fuel usage, but any of these cars with an automatic and I reckon you will be back to square one, if that makes sense.
BTW, didn't know your 330i was automatic!!