Just a quick update today - I've just driven home in my new car and I'm hugely impressed. It's a Toyota Auris, which is a slightly smaller version of the Prius but with the same hybrid engine. It's quiet, comfortable to drive, does 65MPG and has a usb interface for my iPhone.
The coolest feature is that it monitors your driving for eco efficiency during your journey, and when you switch off it gives you a rating. On my trip home tonight I earned an excellent - BEST!