Andy Hayes and I did a survey back in the 1970s. It did not get published because parts 2 and 3 of our Matlock books were rejected. The extent of workings is shown on an area map in Vol. 1 of the Mines and Caverns of Matlock Bath. There were also various very rough partial plans made in the 1950s.
The Long Tor survey will of course be published in my new book “The Matlocks: Mines, Caverns, and Thermal Springs” – if the PDMHS are so inclined. I am still waiting for things to happen in that direction. Its text is now sufficiently rounded out not to require any more research but new stuff still comes up from time to time. Though I say it myself, it marks a staggering advance in our knowledge of the Matlock mines (this is also the opinion of other readers of the draft).
I had always hoped that some bright spark would extend the Long Tor workings – either a dig behind the steps in the entrance stope or at the collapses at the north end. There is also the coffin level sough that used to exist under the old Whittaker’s mineral water factory – no-one has been into that in living memory (at least, not that I know to).