There are two shafts I know of higher up in the woods, one already capped, one open with partly collapsed ginging.
Doing a thorough investigation is a worthy venture, but speaking from my own experience it's best done in winter when the vegetation's low so you a) don't miss shafts, particularly ones with slumped beehives or b) find them by falling into them. Also, might be worth giving the new owners a copy of Mining History 17:3 with its full survey and description of the underground workings?
Follow the horses, Johnny my laddie, follow the horses canny lad-oh!