To be honest, we took the N road from Nantes to L'oree du Bois in 2009 in order to avoid tolls. We had previously travelled on toll roads. Having experienced delays through towns and villages behind lorries which had the same idea, we would prefer to pay the tolls and get there a bit quicker, without the traffic, going down to Saintes and then across to Royan.
With regard to the site, we arrived just before 6pm. We had trouble finding a pitch without dog mess on. The shower blocks were not too clean. We moved the following morning to Sequoia Park where we had been before knowing we were guaranteed a good choice of pitch and an enjoyable stay (this was Whitsun ie. low season in France. If you are looking to go camping cheques and in low season, there have been good reports on the site Le Bois Soliel just south of Royan in St Georges de Didone.