The starting point for considering risks around Covid has to be the arrangements between a team, its crew and drivers.They would consider the advice from Gov.uk, MSAuK, BARC, MSV and effectively make their own risk assessment.
The club is promoting the race entry and then provides details of those to BARC and MSV. The drivers will need to self certify to both BARC and MSV and this will place responsibilities on them if they have any symptoms of Covid. Emails will be going to them shortly we expect and I would assume they will share these with all their team, we are expecting that the drivers will need to provide details of the crew (their 'guests').
The club will not be involved in the approval process other than to provide a list of the drivers. If BARC or MSV were to not allow a driver to participate then the only involvement of the club is that we have advised all entrants we will not make a refund.
In relation to foreign drivers then they can participate assuming they can satisfy BARC and MSV.
Spectators will need to meet MSV ticket entry requirements. More here
http://www.msv.com/media/7316006/how_we_are_keeping_our_customers_safe_at_race_meetings_-_august.pdf