Hang on chaps.
It's very difficult to classify the above as "fraud". In fact it's easier to classify Kev's letter to the bank as libel!
The fact is that Silverstone intended to charge £30 for parking, as evidenced by their website. Silverstone appointed Vinci as their agents to collect that charge and for whatever reason Vinci are now seeking to recover that £30 from Kev with no surcharge, so long as he pays within a fortnight of last Friday.
Personally I wouldn't go anywhere near Silverstone, as I won't pay their ticket prices, but turning up and then labelling a perfectly legitimate charge as fraud is out of order.
Yes I reread the OP, and you're correct, i had thought this was a scam. However, seeing as kev was "herded into a field" and nobody saw fit to take any money off him at the gate nor was there any apparent signage advising of a requirement to pay, nor were there ticket machines, then please advise where is the basis of a contract?