I am in France for 14 nights next month. Had struggled to get into the site I wanted but a friend's parents have holidayed there for past 35 years... so they phoned owner on my behalf. They agreed I could stay day 7 - 13 of the holiday there. Even though I've to move ouch mid week. Ihave opting for An aire near Cherbourg on the last night.
I then set about trying to get a site for days 1-6. Almost impossible. I finally got where I wanted but have had to book in for 7 nights even though I'm only gonna be there for 6. The booking site is showing fully booked but onringing the site direct I got availability so long as i agreed to book 7 nights.
Just my experience, but I'd recommend booking.