What's the annual mileage limit on that?
One point to watch is that classic car policies normally don't have no-claims bonuses, so if you switch back to regular insurance in the future you may have a problem proving your complete NCB record. Also some classic car policies expect the car to be garaged (which of course is fine if it is).
When I worked at an insurer I read about a guy who claimed for a Ferrari theft and it was supposed to be garaged. He said it was because it was in a multi-storey parking garage (which he owned!). They refused to pay, partly for this reason and also because he left the keys with the attendant in the payment office.