Two years ago me and Alex from the TSG went down Merlins to pick up a water sampler - we had to also pick one up from the further reaches of Carlswark so decided to try the through-route, not expecting to manage it - but we did, and it was pretty easy really. After picking up the water sampler we exited via the Gin Entrance and strolled back to Merlins to pick up our harnesses - which were at the bottom of the shaft. Erm - now you tell me. Anyway, I was able to free-climb down it pretty easily if truth be told, and after tying the harnesses on the rope, free-climbed it back up again. But obviously I couldn't possibly recommend that approach as I've screwed up a few free-climbs too.