Going on some hazy memory here so I can't guarantee any accuracy and might have the middle section mixed up.. :?
From Lost Johns, heading upstream climb up boulders around Lyle Cavern and find crappy rope climb and a pitch going up. At the top was a crawl over a pool, which enlarges (nice formation) and reaches junction with bigger passage, headed left and somewhere along there is the rope climb down.
Following passage to where it bends sharp right take passage on left (which is on the corner), could then be the low blasted rock arch to a crawl in a pool exiting that on the right. There is also a faffy climb to get up too.
After that it was following passage past some holes in the floor, I think it was more or less straightforward from there, it did drop to a crawl which was followed to where it pops out on a ledge (marked Kendal Extensions on that Boxhead rigging topo).
:up: HTH, Dunc