There are many other classes, such as the Superkart gearbox class shown here. These 250 twin cylinder six speed gearbox karts are more at home on long circuits such as Silverstone and Brands Hatch.
There are also classes at the top end of the sport that run in National European and even in worldwide competitions. These classes are not normally seen at club events except when a championship round at the circuit is imminent and the club meeting is used for practice.
There are other four stroke classes too, such as Honda senior, but these do not generally compete at BPKC race meetings.