Where is the campsite La Chesnays?
By Car from the north:
Leave the A10 at Saintes (J25) follow signs for Royan . Find the Bac (ferry). Crossing of the Gironde is about 30 min. Watch out for queues in high season. Follow the N215 to Soulac, then the D101 to the campsite.
By Car from the south:
Leave the Bordeaux ring road (junction 8). Follow the RN 215 passing Castelnau de Medoc and Lesparre. Then left at the D102 until arriving in Vendays, take the D101 at the lights towards Soulac. The camping is on your right as you leave the village in Mayan.
Bordeaux Airport is "International" with regular flights from the UK and Europe. Plenty of car rental. If you fly yourself, there is a small airport open each weekend: Aerodrome Montalivet.
Bordeaux is connected to Paris by the TGV Atlantic. The ticket will get you as far as Lesparre in the summer. Then take the bus 15km Vendays-Montalivet.