Hi Miles. With membership you get a quarterly magazine, club discounts for tickets at events such as the Silverstone Classic, plus a guaranteed display space for your car (if it's a stratos, naturally) , member garage open days. Most of these guys are amazing mechanics with a wealth of knowledge for builders, club merchandise, a member's only forum and first dibs on parts offered by club members.
It's a great little club. Full of really friendly and helpful people. The Silverstone weekend is a highlight of my motoring year.