One of the reasons that I have never tried to enter is the Toff's fashion parade aspect... just too much posing.. though I have been as part of other people's equipes.
Now, period clothing, how about French 'bleu de travail' (blue overalls) greasy hands and beret and a Gauloise all topped off with garlic breath? Maybe that's not the type of 'period dress' thay are thinking of, surely there must have been French mechanics at the Talbot pit??
Sadly I will not be there this year.