In reply to Matt438:
You could do worse than do what we did a couple of years ago. We camped, but at refuges, and ate the food they made.
Day 1 - GR10, short
Merens Les Vals (train station - on the line to Barcelona from Toulouse)) - Refuge des Besines.
Short and steep, with hearty refuge food when you get there, and sulphurous pools on the way up.
Day 2 - GR10 long, flat
Refuge des Besines - Refuge (chalet) des Bouillouses
A stunningly beautiful high mountain day, most of it at around 2000m, I think, ending at a lake with a dam. A great cook at the refuge.
Day 3 - not the GR10, but a way marked route : Carlit route, or something? Quite long but really lovely.
Refuge des Bouillouses - Enveig (train station - end of the line that you started on)
We were aiming here for a campsite, but in the deluge that engulfed us as we descended, decided instead to go for anything with a roof. We had a very convivial night and meal in a chambre d'hote.
You could skip the third night if in time for a train and head back to your start point at Merens, which itself is only 10 minutes or so by train from Ax-les-Thermes (more of those warm, sulphurous pools). If you are to stay there, I recommend the little hotel on the market square, and to do so so that you wake up on market day.
edit: Days 2 and 3 took us more than 6 hours, but we are in our 50s!
Post edited at 16:03