Make sure you state your average mileage when you renew - pointless paying for ten thousand miles if you do four; make sure you insure for social, domestic and pleasure only, you don't need to be insured for commuting; increase the excess to the most you can comfortably afford.
Shop around and use the comparison sites - but don't forget to look at the companies that don't use them, such as Saga and Direct Line.
All this should make your fully comp insurance as cheap as possible.
Another possibility is the 'pay as you drive' type of insurance that needs the insurance company to install a black box tracker.
http://www.confused.com/car-insurance/pay-as-you-drive