Folk singer

[paije]

A large lady from a few years ago she sang folk music about mining and coal miners in Wales

[dr pop]

Rita MacNeil - most famous song Working Man??

[WeeAngie]

Or maybe Brenda Cochorane XX

[littleoldme]

It does sound very much like Working Man, originally written and sung by Rita MacNeil, although as she is Canadian, so I doubt she was singing about Welsh miners. She certainly also fills (no pun intended) the "large lady" description. The song has been covered by a number of people since.