In reply to Dave Turnbull, BMC:
I'd expect it to be fairly dry at the moment, but it's OK when damp anyway. The start is pretty unmistakable. Go down the descent gully (definitely use a rope), turn right (looking out), follow small track through the undergrowth, brings you to the bottom of the main buttress just right of TNW which starts up the obvious chimney corner just left. Left of here the path continues immediately next to the face, until you get to a big tree where it turns 90 degrees left which should alert you if you've gone too far.