You've not done your research here. Unless I'm wrong, in which I apologise.
Class 1 - Beginners - engines up to 1000cc - suggests AX or Mini
Class 2 - Beginners - max engine of 1300cc - loads of cars like 205
class 3 - "big engine" inplace of the original - And still MAX of 1421cc
Here is the link
http://www.national-autograss.co.uk/...autograss.html
EDIT there is 9 classes, I aint reading them all....