In reply to gammarus:
When I did it last year (30/Apr/18), there was some tat higher up, meaning my ropes wouldn't touch the ground (30m), but realising this in time I pulled them back up and continued down a little further and found some more tat a little lower (20m) and went from there. I also abbed off a hanging slab on the Garbh Choire side so the ropes would pull more easily (quite scary).