By way of comparison, after 8K miles the 328i is doing around 38-39 with 'normal' driving - that's 50% country lanes, 25% dual-carriageway/m-way and 25% town. On a long m-way run it'll return a shade over 50mpg at a steady 70-(ahem) which is pretty impressive. The scary bit is Sport Mode loony-style where it'll drop to around 32mpg.
Incidentally, these figures are all with the aircon mostly 'ON' if that makes a difference.
340i in Estoril Blue