I guess I ought to pipe in here as I suspect that there won't be many others on here who have been to the end of Sandy Hole, and even fewer who have been there more than once. Unfortunately the survey has never been published, but I have just made a very rough measurement on Google Earth that shows that the southern end of Sandy Hole (or at least where it was radio located to) lies just over 600m south east of the Sandy Hole entrance to the system (Sharbutts Rift is a little further north and the Blacknor Hole entrances about another 450m north. Clearly the distance covered in the cave to this point is somewhat greater than that, but by how much I do not know. I would hazard a guess that there is c.2km of passage south of the old Ammonite Passage choke, but there are several branches. Never the less, it must be at least 800m of continuous crawling to reach the end. There is only one place you can even sit up, the Inkwell, which is only about 5-10 minutes inside the entrance.
From memory it takes about 4-4.5 hours of crawling to reach the end. Much of the crawling is between hands and knees and flat out, and is largely over muddy angular breakdown mixed with copious fragments of chert. Its quite strenuous and thirsty work and most people develop a thumping headache within an hour or two being in there, possibly due to the head down attitude for an extended period. Describing the end as "Wide Open" is a little misleading. I have not seen the current end, but did see the end as it was 20m beforehand. In this case the low, wide passage was almost totally blocked with large breakdown. On the subsequent radio location trip I was fortunate enough to be the only one who knew how to operate the surface kit, and was talking with the guys underground when they dispatched one of the boulders to get through to another 20m or so of passage leading to a similar choke. I asked the guys as they reached the end if it was "terminal" and the reply I received (with some relief) was "yes, as far as I am concerned". I am sure that this choke would go quite easily if dug, if anyone can be arsed to drag the necessary tools into the cave.
As to flooding, there is no risk whatsoever in Sandy Hole. The myth of flooding comes from a speculation in the Portland guide about what would happen if Sandy Hole continued south toward sea level. The point being that Portland has quite a high tidal range, and the cave follows down the dip at 1.5 degrees on average. It was postulated that in the inter tidal range that the waterlevel would rise up the passage faster that it is possible to crawl. This remains nothing but a theory as the end of the cave is still significantly above sea level as far as I am aware.
I have also not heard of any further pushing of this system this century!
