Souter Hole seems to be in the news, a small hole having fairly suddenly opened up into a 40-foot sinkhole with a beach at the bottom.

The National Trust have fenced it off to stop people falling down it.  I don't know what access there is for cavers, or how much there might be to see down there.

Edit:  though it seems there was a warning about it on the BBC news back in March 2019, when it was a mere 13 feet deep...