If you don't need 4 seats Smart cars are a hoot. The new style ones can be had for well under 6k now and belie their size - I had an older style Brabus coupe (the upright one, not the sporty go-kart one) and it was simply one of the best cars I've owned. Put more miles on it (motorway too, including a few very long drives abroad) than any car I've had. Loads of space inside, a big boot area too (far more than the Aygos of this world) and great performance. You could pick up a Pulse Cdi for around 6k and it'll cost very little to run.