They had loads of problem hiring coal miners. Which is why slavery in Strathclyde lingered for so long and had to be banned by courts as late as 1774 - miners were bound and being bought & sold along with the mines. Free men wouldn't work there. Through the 17th & 18th Centuries, coal-mine contractors got their labor by emptying out prisons and poorhouses, capturing vagrants and beggars, etc. forcing them to work the northern mines. Which is why there was so much female and later child labor in the coal mines. You could pick up orphaned and abandoned children by the cartload from the poorhouses in the south and bring them north on compulsive apprenticeships.
Coal mining was always the "bad boy" of English industry. It has an awful reputation for good reason.
But even so, it wasn't as bad as sugarcane.
How Green Was My Valley