What's the best car for a driving instructor?

My wife is a driving instructor and is considering replacing her three year old Toyota Yaris (petrol). Most driving instructors appear to use diesel cars but with the inevitable short journeys and stop/starts...

Buying a small car for £10k - what's best?

I have a budget of between £8000 - £10,000 to spend on a nice small car for my wife. What do you recommend I buy?

Which cheap small car?

I am looking to buy a new car with the following requirements: economical on fuel (running round Cornwall), reliable, small, and under £10k. What is best?