I think all mining museums have these sort of problems.
Robert & I helped, a little, with the setting up of Florence museum.
The atraction here was it ran underground tours, but once the plug was pulled on the pumping, it closed pretty soon afterwards.
Even with underground tours, and no pumping required the Wanlockhead museum has struggled to keep going.
Basically whilst we all think it is a fantastic idea, the great British public want to entertained, for their money, and I am not sure how you can do that underground, easily.