If you go on the ACSI website and look under camping card, you can look to see which sites give discount on any particular date. For instance, I entered 17th-18th Aug for France, and there's a number of sites dotted round giving discount.
I would check the weather forecast when you arrive, then head for the sun, but slowly, as the less popular sites further north are more than likely to have spaces. And as each day passes, there'll be more and more, and more further south.
We have never been this early, but this year we will be, so that is our strategy. We never book, but always have a contingency plan.
I wouldn't book, but then we never do, and it can be a bit daunting to those who are used to booking months in advance. If you feel uneasy then ring the day before heading off somewhere, and check that they will have space. If it sounds at all doubtful then ask if they will reserve a pitch for you on the day you want to arrive. You'll know from the reaction of the site reception staff whether there is going to be a problem or not.
Had our first non booked full holiday in May courtesy of camping cheques. I feel more comfortable now having done it once. It was lovely not needing to chose a site until we actually got to France and started chasing the sun.
Good luck wherever you end up.
------------- John
May/June.....France
Aug.......somewhere else in France
It is a bit scary the first time you do it but it is more reassuring if you do some research in advance and have an idea of what sites are in the area(s) you hope to visit. It also has the advantage that you are not committed to staying on a site if it fails to meet expectations once you arrive or that you can stay as long as you like if it exceeds them.
Don't forget to leave a review of the French and other European campsites you have visited!
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.