If it's not Peak Cavern but is Derbyshire, is there any possibility it could be somewhere in Giants? There were some very pretty bits in odd corners above the main stream both upstream and downstream of the old Pillar Crawl and before you reached Garlands.
If it's GB, so on Mendip, then the finely decorated chambers reached by climbing the ladder at the end of the streamway weren't found till quite late on were they? I was there before the "Great Flood" of 1968, probably in 1966 or '67, but don't recall seeing anything like this and had the impression then that the new chambers hasd been found relatively recently.