It isn't usually a problem (look for lait pasteurisé) which usually comes in bottle with a blue top if you like semi skimmed (demi ecremé). Sometimes our supermarket runs out, so don't leave it to the last minute!
My previous experience in Val Claret was that it was never a problem. Took ds when he was small (admittedly the last time we went was a 5 years ago) but the supermarket always had fresh milk - we were certainly never without it.
Which part of tignes? We were in val claret. The supermarket was pretty well stocked although small. I didn't particularly notice fresh cow's milk, but they had quite a large fridge section with soya milk and yoghurts, so I'd imagine there was cow's milk.