In reply to ebdon:
The OP's 'couple of slightly less experienced friends' might well have kittens on Avernus. If anything happened to the OP, they'd be well stuffed. Both my partner (a leading Welsh guide) and I felt that Avernus is a serious proposition. We did it in drought conditions; if it was damp, it would be even more serious. Rubbish pro. Awkward route-finding; on one pitch, if you go the wrong way (and it's not obvious), again you could be stuffed. Wouldn't be a bundle of joy to retreat from, either. Hopefully I'm not selling it to the OP and his mates.
Mick
P.S. It's a long way up and a long way back down again. Paul Williams wrote something like, "collapse gratefully in your car!" and that's pretty much what we did.