Everything is governed by the MSA blue book. Download the latest one here. (Enter the search ‘yearbook’ to find the latest.
2020 Version here: motorsport-uk-yearbook-2020
2021 Version here 2021-01-11-motorsport-uk-yearbook-2021
Section Q governs circuit racing 2021-01-11-motorsport-uk-yearbook-2021-p283-303-specific-regulations-circuit-racing-q