Race Track visits

Hi all.
A couple of weeks ago I had a day spare ( midweek ) in the Milton Keynes area. So I thought about a visit to Silverstone. I checked at the local tourist information and they explained that midweek was a problem as Silverstone has no visitor centre or museum..Now I know that Croft Autodrome also has no " Tourist Attractions " ( Its my local track ) And I think " Donnington has a Museum, But what about other tracks. So which are worth a visit midweek, non race days ?