Hi Barney,
I will be travelling Dover / Dunkerque on 15/10/2006 and then down to Spain. So it will be around the same time as yourself. I am not booking any sites at the moment, just taking the Caravan Club Europe book with me and search for sites which are open as we go along.
First night I will be stopping at Castels site at Guines as I am sailing at 4pm from Dover.
I would not worry to much, plenty of places still open at the "end of the season"
Safe journey,
Dave