Hi Pete, welcome to the site.
Considering that you live in one of the centres of the world insofar as holes in the ground are concerned, you live in a fairly rubbish place for mine-exploring! ::)
There are a few on here from the Swaledale/Wensleydale areas who pop up every now and then otherwise I'm not really sure what else is about. A few groups of us are active in the Cleveland/North York Moors part of Yorkshire but half of the Lakes, the Peak & Wales are probably more convenient for you out there!