In reply to ste parry:
Did it a few weeks ago, and I agree, the slog back up to Prarion is hellish, especially in the heat of the afternoon.
I did think of driving around to St. Gervais, but it's a long way compared to Les Houches. I have got on the tram no problem in the mornings, but have had a game getting a reservation for the descent. This year we had to wait, but it was only 90 mins. Mind, I wouldn't have wanted to be one of the tourists on a day trip, crammed in with us stinking climbers.