Just wanted to mention that the latest edition of the Cwmorthin exploration guide is up on the Cwmorthin page. It shows the position of all the technical bits (pitches, tyroleans, traverses etc) in both veins. It has no historical element and doesn't need it with Grahams excellent composite survey already available.
If you like to explore Cwmorthin then I hope you find it useful!
Miles
Beneath my steely exterior beats the heart of a dashing hero