As I mentioned in a comment yesterday, I probably was a bit hasty in reporting the fantastic mileage of the cars on Top Gear on Thursday. I sorta knew there was something called an "Imperial Gallon" (aproximately 4.5L, as compared to approximately 3.8L for a US gallon, according to wikipedia). So the MPG the Top Gear guys quoted has a bigger G. If I use imperial gallons for my mileage, I think I am up around 50 MPG highway, and around 36 combined. Not bad.
Still, that VW Polo diesel is pretty impressive.