+1 for Blockley's, they are a popular and well proven upgrade and the same price as the Avon's

They're available from MWS Wheel Services (who supply MMC) http://shop.mwsint.com/product_details.asp?id=119

The Coker Excelsior Comp. 400H19 from Longstone Tyres are reportedly similar to the Blockley's in cost and performance

If you want to go for more performance then people have used a number of motorcycle tyres which provide much more grip but at the expense of tyre life. See the Alternative Parts List.

Red Leader drive