So is £340 your budget?
I've just ordered an F20 125d with about £3k of extras and that is exactly what it's costing per month on a PCP at 14k miles per year.
You could probably drop to the 120d which will still be quick enough to be fun. The auto is very good but it does add around £1500 to the price. I'm not sure what figures people are getting out of the 120d but according to reports 50mpg is easily achievable in the 125d. not bad for a car with over 200bhp that does 0-60 in 6.5s
While looking for a car I test drove.
Same performance as the 125d but way more expensive to run. It didn't drive anywhere near as well as the BMW.
New Audi A3 1.8tfsi.
Gearbox doesn't seem to suit the engine. The engine was good on the motorway but crap around town. Handling and ride is much improved over the old model.
Just boring, felt a bit dated compared to the above and wasn't cheap
Skoda Octavia VRs
Same engine as the Golf but drove much better. I believe they don't share the same suspension set up or the Octavia has that complex dif thingy from the Golf GTi or something. MPG reports aren't fantastic for a diesel and my wife's a snob so it was out from the start.
Ford Focus 1.6TDCi
It drove well but I hated the interior.
Only other thing that I can think might be good is a Mini Dooper or something. Too small for me so never even tried.