Hello Roy,
That's a coincidence, as a small group of us visited Hanging Flat last Tuesday 20th. Worked for fluorspar in the late 1970s / early 1980s (Info from C of the PD - 2010 Edition).
The first time, I explored the mine, wooden doors were in place at the entrance, can't remember the year.
Re: Peak Practice - On a previous visit, I placed a laminated information pouch(including copy of cutting below) in the mine for the benefit of future explorers (Sadly water has penetrated the pouch, but I will get it replaced).
In one of my scrap books, I have a cutting from 'Radio Times'(I think) advertising actual episode and including a colour picture underground in one of the locations used. Episode was in Third Series and titled 'Light at the End of the Tunnel' and featured Kevin Whately! Shown on Tuesday 31 January, but no year on cutting!
I do have this episode on VHS, but could do with transferring it to a DVD. Noted that Peak Practice is presently being repeated on one of the many channels.
Cheers, Paul.