Andy, the Racing Drome has been closed for a few years now (ten minutes from my house). As Darren says, DMS run on Thursdays indoor, Aylesbury on Fridays indoor and if you fancy some dirt action get to the Proline Indoor Dirt Arena on a Wednesday. .......... but you can't run your yellow minipins, has to be Proline. Numbers are growing every week and the competition is tough, with national A finalists/winners and Euro A finalists attending regularly. Maybe not quite what you're looking for but worth considering?
