over here mostly everything is open class. you get the pro class and the support class for the british, nett, irish and scottish championships but they are all still open class, you just need a speial number plate so the officials no what cc you run. yellow back ground number plate for 450cc and under and a white background for anything over 451cc.
the only race over here that has a cc class is the Weston Super Mare beach race in bristol, england. its an international race and hundreds of 2 wheelers and quads turn up for it. of course quads race quads and 2 wheelers race 2 wheelers but all done in `cc` classes until the end when they race all the quads in 1 race and all the 2 wheelers in another.