Re: Pathfinder idea...
Yes, on reflection over an hour is of course way too long to leave it... 15-20 mins would be fine (unless it was a 16v in the mood for being driven!
Shame it is 'so late' in the year, I agree. But it has been carefully considered given the following factors (based not just on my experience but also upon discussions I have had with a contact connected with arranging French holidays):
Summer vacations for most in France are over by end of August. Those families without kids either do before August (or even before late July) or for the first two weeks or so of September. Prices for and availability of crossings start to drop off after then too in general.
For those with kids, the last two weeks of October is often a half-term. Also, this isn't necessarily always the case in France, so the roads should be OK. I chose a Sunday for the first day (a 300 mile stage) as the number of HGVs on the road are much, much less than other days.
Any later, and we're into November where snow really would become an issue on the elevated stages.
So I plumped for 18th Oct. Still nice weather usually and not too hot or cold.
The date's still 18th October.