In reply to Spike:
If you go for the lac Blanc option it is a cracking place to have a night at the hut. Arrive late afternoon, quiet beer on the terrace, then a 3 course meal with wine in the evening. Then off to the Col du Montets, maybe up to the Col du Belvedere, or retrace your steps to the lift the next day. Did this with the present Mrs HammondR a few years ago and she loved it.
Be careful with any of the lift options other than the Midi as many of them close at the end of the ski season, and only reopen in the school summer holidays.
Other good trips over there are to go on the panoramic lift across the Valley Blanche to Helbronner from the top of the Midi (or go under the tunnel to Italy and go up the new Helbronner lift), or take the train from St Gervais up to the Nid d'Aigle with corking views of the Bionnassay aspect of the range.