In 1977 we were privileged to stay two weeks at the Danescombe Mine, in Calstock, near Plymouth.
We loved the area, and it prompted us to leave London and move to Devon.
The Channel 4 series on the Landmark Trust shows many of their properties being restored, to become holiday homes.
The next episode, I believe, features 'our' mine:
www.channel4.com/programmes/restoring-britains-landmarks/episode-guide