Right... if you leave your current insurer now you're basically down £445 for the rest of the time the policy would have run until. So to get a better deal elsewhere, you need to get a quote of £755 or cheaper by my reckoning: that's the extra £1200 you would have had to pay minus the £445 you'll lose by leaving them.
So do you think you can get a quote of £755 somewhere else? You should be able to at that age surely?
Try Keith Michaels, or other specialist insurers. If trying Keith Michaels, ask if they have member of the sales team who specialise in Cosworths. All the phone numbers are here
http://www.keithmichaels.co.uk/conta...-insurance.php
Gary Moulson, for e.g., is the man to speak to for Subarus and can get you a better deal than the other staff as a result of this, so there might be someone that can help with Cosworths.