I went from a BMW 335d M Sport to my Golf R32.......
Personally, if you want economy AND performance, then you need to spend a lot of money to get something that will still be fun to drive. My 335d (work car) was superb. Chipped it, and was running 350bhp and 730NM torque. But best of all, it still averaged 37mpg. On a long run I would see 40-45mpg.
I do miss the oomph of the BM, but the sound of my .:R is beautiful. Yeah, the 20mpg is a bit of hit, but who cares. And I still do nearly 20k per year.
For the mileage your doing mate, stick with a Petrol. Honestly, think you'd save pennies rather than pounds overall.