I could make it down for a day from SW Scotland, I've looked at Copperplate Mine before but thought it was too difficult to get into?
Goldscope, Carrock (we'd need an adjustable spanner for the gate now), Coniston Slate and Copper, Seathwaite Graphite, Greenside (if we could find the key!) Rachel Wood at Thornthwaite (the Forestry Commission have it I think) are all good possibilities for a visit.
Or there's always Nenthead 😉