welcome fellow brit..............was going to point out early, b4 u make a mistake, avoid the petrol engines......

go for DIESIL

MPG MACHINES THE 520d, Like
500 miles a tank plus, petrols will give maybe 350.......

so go for the diesil, plus they have more power like for like, more so on the 520i to 520d, plus you can remap and get upto 30% more power and upto 15% more mpg economy

good luck anyhow