Focus has been suggested so i'll throw another in to the mix. Mk5 Astra SRi 1.9 CDTi 150 XP.
If you ask me as nice to drive as the Golf/A3 a remap can see best part of 200BHP.
My sister has one and it happily returns 40MPG all day long and better when on the M-way.
Try hold out for one with leather there heated too. Quiet rare to fine a full spec one.

http://www.autotrader.co.uk/classifi...1501?logcode=p