Theres never much in the way of 'information' about deneholes/chalk wells as they were dug long ago and were of little to no use once worked out, countless holes have been filled or capped with probably a lot remaining undiscovered, they were apparently given a sort of brick dome capping (where they were capped at all). One of the few accessible (though gated) holes is near Hucking, it was cleared a few years ago by KURG and is about 40 feet deep.