Hows about targeting/e-mailing caving clubs in those specific areas?
I know that caving clubs do have members that enjoy mines as well as caves.
Maybe a nice email formed in the style of an advert, pictures etc, rather than a few lines of text and a request to post a mention in their links page?
There is a list somewhere on the internet of registered caving clubs in the uk, with contact details and where relevant, e-mail and web addresses, albeit sometimes out of date.