Hi andy,one of the most popular ferry routes is to santander bilbao direct giving a shorter drive down to warmer climes..there are discount codes available I believe if you ask the right person.C&CC will give you a 10% on these routes so may be worth looking into.Can't afford that myself but we enjoy driving down via calais.Get a copy of campercontacts app on your phone/tablet to assist with finding a stopover enroute,As well as excellent sites on the clubmotorhome motorhome stopovers.
Also most prefer to get the acsi card and app to get some great out of season discounts.If you stay for long enough you may also get better rates withought acsi.We went down beginning of feb this year and found sites filled or filling up for march so maybe worth doing some homework and booking ahead.Bigger is not always better as the best site we found this time had approx 20 campers but all very friendly and eager to talk and share experiences,unlike a well known site in benicassim which is not called little britain for no good reason a lot of long termers seemed very clicky..Above all enjoy it is a great experience.
Not sure what we are doing but definately going down Aug-nov this year through france for a couple weeks and into spain possibly portugal.cheers Pete