In reply to edunn:
There are plenty of suitable bolts to anchor your rope from, and you could get down to the bottom by abseiling with the rope just hanging over the edge, but (in my opinion) it would be very dangerous (suicidal even) to try to jumar back up without having re-belayed the rope. I wouldn't even do it with a rope protector.
The distance from the lip to the floor is ~98m, so a 100m rope is not long enough when you take into account the knots etc.
The main shaft will be very wet, even during a drought. The water hits a ledge part way down and sprays everywhere. There is a route down close to the main shaft which avoids the water (Jib Tunnel), but again the rope needs to be properly anchored caving-style (SRT or single rope technique if you want to read up about it).
I won't even mention permits....(oh I just did!)
If you want a trip into Gaping Gill there is the option of using the winch set up at Easter by Bradford Pothole Club, or around the August bank holiday by the Craven Pothole Club.
If you want a trip at a quieter time send me a PM and we'll see what can be arranged.