Mr Mike, I believe the old mine office is being repurposed as a base for the Moor House Nature Reserve wardens - as we know, it gets very bleak up there in winter (anytime from late August to early June!). They appear to be removing the 'modern' end with its concrete block construction, and doing a proper job on renovating the older part, replacing oak beams and fitting a new roof.
EBGB looking at your fabulous plan, I wonder if that is for the 'other' Silverband Mine on Cronkley Fell, just 3 km South east of the Cow Green Reservoir Dam? Both the Dun Fell Silverband and the Cronkley Fell Silverband mines happen to be in the same nature reserve but the veins appear to be different names to the ones shown on plans held by CATMHS. I shall have to do some research into the Cronkley Silverband mine, but your original plan is rightly a prized possession. If you wouldn't mind I will print a copy off, to do a surface explore over Cronkley Fell way, sometime soon. I also have attached a copy of the BGS plan of the Dun Fell veins from around the 1970/80s for comparison. Note the open cast now extends to probably as far as where the underground shaft is marked, but no further, and it is now backfilled. see below...
Roy, the reference to the lost miner is mentioned in Carl Rogers book 'To Be A Gypsum Miner'. Carl spoke of a colleague called Roland, when working at Birks Hill mine. Roland had moved to British Gypsum when underground working Silverband Mine was in decline, in the early 60's. He was the person who got lost whilst exploring the old caverns and workings. Roland told Carl that he emerged 'on the back of Dun Fell' and if so, he actually stumbled on a through route from West to East.
Given the Opencast has destroyed much of the western side workings I believe like you, that a cold winter's day may well reveal the location of an old entry/exit - if it still exists. I shall be taking a lucky dog for some long walks just east of the Radar Station road, when the cold high pressure days return. There are two branches - one from the Dun Fell Vein workings (near the famous Silverband caverns) and one from the Loppysyke Vein workings that appear promising.