Les Sables d'Olonne..Big town atmosphere..
We stayed at Longville Sur Mer a few years ago ( a bit quieter and just to the south )..
Long drive down but well worth it for the endless empty white beaches..
It's better to go there before the french have their long summer holidays as the beaches and area can become VERY busy.. Before the holidays it is empty further south..
We found some lovely local wine, cheese, baguettes were great for afternoon siesta's. We hired a house 5 mins from the beach..
As for the xenons I would definately check with your Renault Dealer. BMW xenon can be changed for europe ( internal baffle type thingy in the headlamp )..
Be careful because the Gendarmerie are pretty hot on trying to catch english tourists out.