Spent an hour under the Kent countryside one afternoon as I dived into the world of Chislehurst Caves. They are man made caves in the chalky hills. They are also quite impressive and a good place to go when you want to escape the summer heat and humidity. The tour guide was a bit cheeky but funny in the right way and he was knowledgeable, he was just the sort of person you want to show you around.
According to the guide Hendrix and Zeppelin both played the caves, which would have been amazing to see but I guess the sound would have been terrible. Although this was the late 60s and early 70s so you would have been smashed out of your head and not notice.
I would recommend this tour as it was good value and interesting.