In reply to Fredt:
OK. I was advised to take the ladders just after the Charpeau glacier, but I just could not see them. Eventually followed cairns to Les Egralets. The moraine below these ladders is a nightmare, big boulders sliding down sandy rubble. Parts of the Egralets ladders were missing, but linked with fixed rope hawser, the moves and the rope were both pretty hairy.
Coming down I traversed along from the Couvercle and eventually found the tops of the ladders signposted ‘Montenvers’, just before reaching the Charpeau glacier, and descended these to the Mer de Glace. Looking back the ladders were extremely difficult to spot, but marked by a small yellow square on some big blank steep slabs, easy to miss. Not much difference in time, but the latter approach more enjoyable, more scenic, and safer.
Post edited at 07:16