Some of the workings are flats, some conventional, if that's the right term, stope workings, with evidence of splits into branches.
The shaft I mention does cut the high level but its not obvious as at that horizon the downward continuation is boarded over and buried in rubble. Heb is of the opinion that its Sir Lancelot Allgood's Caplecleugh Engine Shaft, and would of course predate LLC. This area may not now be accessible.
If all surface shafts flooded you must have missed one or looking in the wrong place.
Beware ropes up to the high level. I have not been there for ages but have been advised that they in poor condition.
My avatar is a poor likeness.