I wish my car did 30MPG Lee S, I'm happy seeing an average of 24 in my beast!! :-D
I don't really put that many mileage claims in, I only live about 8 miles from work and mostly can be bothered.
I know this trust has different rates for engine size and I they have different rates for On-Call, Return To Work etc.
I tend to worry more about my insurance policy. I keep meaning o look into being paid to drive into work during a call out session.