My sons, both surfers (and the eldest now a kite surfer) love Lacanau Ocean - and have stayed on two sites there - L'Airotel de L'Ocean, and Les Grands Pins - both with excellent facilties.  Les Grand Pins is an 
ACSI Card site and takes the ACSI card up until 25th June, and again after 12th September - so a pitch for two, with car and caravan (or tent), awning, and electricity would be just 15 euros.
	Start with the dates you want - and think about the campsite first especially if you plan to travel during the school holidays.  If you can go outside this time then you really needn't book a site.  My son has just got on at L'Airotel without a booking.  They'd cycled down from Cherbourg over the course of a week and then had eight days at Lacanau surfing.  Then select your ferry route appropriately.  Start looking for a ferry crossing around October, when prices come out, and special offers are available.   The longer western channel crossings are the cheapest - but the western crossings probably more convenient.  The Caravan Club can do it all for you - or you can do it yourself.  M