In reply to Babika:
Depending how late you are in September the refuge des Ecrins may not be open but there is a winter room. It's a high peak to do late September but with decent weather should be fine. The rock is OK on the ridge, if there is fresh snow it will be harder. The Voie normal is a glaciated north face until you get to the col where you join the ridge, so crevasses can be an issue late season.