Based as you are at Bournemouth, I am suprised that being so close you have'nt considered spending a day exploring the Isle of Purbeck to see what remnants and ruins, if any, can be found of the former industries of limestone quarrying (some of the stone was mined underground) and china clay extraction? I clearly remember a working clay mine being on the Isle of Purbeck in the early/mid 1960's, it had a small single rail track bringing the clay out of the mine, which was then taken to potteries in Poole, and made into the salt glazed sanitary ware that builders then used in their groundworks.
I have a small book "Purbeck Underground" by David Pushman published by David Pushman, Langton Matravers, Dorset (date not given, but I bought my copy in 1998, so obviously printed before that date). A lot of the writing could be condensed, but the book contains basic information (including a Bibliography at the end) which can be used to explore and discover an area (i.e. the Isle of Purbeck) containing underground workings much nearer to your home than you might have envisaged!
If you do intend a visit to Purbeck, can I suggest that you call into your local libraries both in Dorset and Hampshire and carry out some research, Purbeck has a vast amount of history still awaiting research and exploration - you might be suprised what you discover!