Hi folks
I worked in Chalk mines for years.
The fact no trace on maps can locate or tell you what you have discovered is interesting and gives me the impression that the stucture maybe..................? ww1 or ww2.

Ebbie Deneholes are made of Chalk the word come from the word Dane.
Alan smith. Its not a Denehole.

If you want to get to the bottom of this then arrange a date and I will come down we can meet up. And get to the bottom of it.
I have no fear of the unknown when it comes to being underground but caution is very important, if one values there life.

We can all sit here till the Cows come home debating what it might Be. Get down there and find out or if you want someone who is used to such Adventure. I UP FOR IT LIKE BIG TIME.. PM ME IF YOU ARE INTERESTED.