I dunno about British series but from the official website the meeting is confirmed. No spectators any time, no passenger or instructor during free practice but no sign of cancellation.
http://www.spasixhours.com
Free practice will be mandatory or not but each session is € 200.
As to travel in Belgium, new rules TBA from 1st Sept.
https://www.info-coronavirus.be/en/faq/ Other infos available in Flamish ATM…
I'm sure Martin can help here.