Steve, I see we're talking UK here, Don't think you'll get a definitive answer on that one. I've taken stuff at low level motorsport events then offered the pix for sale, directly by tracing the sponsors shown on the cars or by putting up a web page and posting on a user forum for that particular motorsport, never had a great deal of sales and in the end not really worth the effort.
Most lower level event organisers actually charge a photographer for the privilege of taking and selling pix at an event, the photographer then has "sole" rights to selling pix taken and they get very upset if someone starts to take sales from them. Even the larger events have an "on site official" photographer who is usually known to all the teams and drivers so sales are easier, or in the case of "press" protographers, a pass has been issued to an "accredited" photographer representing a specific publication or agency.
It's worth applying for "accreditation" to the event organisers beforehand and explaining who you intend to sell pix to, at lower level events, the organisers are often glad of the publicity - but don't expect to get a press pass for the GP or similar!
You are on dodgy ground here at the moment, the event is not held in a "public place", the venue is owned by someone and you've probably paid to enter, you'll often find in the small print of the ticket or program a clause prohibiting "commercial photography", ie selling ANY pictures taken at that event, but if you're sensible and not greedy, it's probably not worth anyone trying to bring a court case against you..... but then I'm not a lawyer so don't just take my word for it!
Stock libraries are getting tougher about releases, mine now won't accept anything taken on private property without a release of some sort, if your pix show a driver who could be recognised then a release IS needed.
HTH,
