/ Pyrenees Camping
The camp sites actually situated in Luz will be as busy as hell.
If you still have a little energy left, I'd continue up the valley beyond Gedre and camp at the Pain Au Sucre :
A really pleasant site- a mate has a chalet here.
If you really want peace and quiet and no facilities at all, there are two places to camp on the road up to the Cirque de Troumouse, near Héas.
"Camping a la Ferme Chez Ernest" and a small camping situated near to the hamlet of Héas. Small pleasant café/restaurant.
Finally, if you have plenty left in your legs : http://www.aubergedelamunia.com/
Situated at 1800m, on the road to the Cirque de Troumouse. Authentic local cuisine ( garbure, lamb / magrets grilled in the chimney).
I recommend the campsite at Le Pla, midway between Mijanes and Querigut. We discovered it one summer when trying to escape the heat of Narbonne. I still remember waking to the sound of birdsong in the beautiful mixed woodland of the Donezan. And you get to cycle up the Port the same way that the Tour has done in recent years.
There are other great cycle routes in the area, including a circuit taking in the col de Jau.
There's a lovely, if popular, walk up to the Lac de Laurenti that you can do from the site, too.
It is on the other side of the Port de Pailheres from Ax les Thermes, however.
There are a number of campsites on the outskirts of Luchon, all ok,
There is a lovely campsite c. 3km up the Tourmalet road from St Marie de Campan. The attached restaurant is superb and it's in a good place to start the Tourmalet the next morning.
The municipal campsite in Luz is functional but a bit joyless. There is a great gite though.
If you have the time, continue to Laruns via the Col d'Aubisque, not to be missed.