The new visitor centre, from what I saw a couple of years ago, may mainly be to preach the creed of how it is so wonderful to no longer have to work in hell-holes like the place beneath due to the area now being "Britain's Energy Coast" and a "leader" in all things nuclear, wind, solar and tidal.
There have been several missed opportunities over the past decade or so to develop a mining museum. For example - selling for scrap dozens of arches donated in order to create an "underground experience" because "they were rusty" ::) might hint at what the completed will or will not be.
Don't worry about the subsidence - it'll be a few years before that affects anything. The whole coastline has been eroding for centuries and the "thousands of tons of spoil" supposedly causing the damage is a red herring spouted by the local council to blame someone else for what they can't stop - i.e. mother nature. The spoil is only moving because they moved most of it onto the already shifting areas when they took over and cleared the site 20 years ago.