I've popped down there regularly over the the last few years with groups (there is a very entertaining duck) and always run down ahead to check water levels. I have had my feet wet almost instantly on quite a few occasions when I would have been convinced the water levels low enough to at least get into the main chamber or even the passage.
I believe that the lower series will stay full for quite some time after heavy rain and is very slow draining. I've not been lucky enough yet to be down there as the water is rising to see how quickly it does so.
The draining of that particular bit of cave is interesting. I imagine a lot of the water will seep out through the infill from the old tip on the surface and collect in some so far unknown draininage channel below the road level. A few years ago a detected a gurgle al the lowest point in the passage to the sump. Water was running away down a small gap between the roof and the mud bank. I spent several hours turning this slot into a a liquid chocolate pond without any conclusive idea about where the water went to. I think there is a little more down there than is currently seen.
The hole in Oyster Chamber that links down to the Resurgence Entrance had water ponded to within about 3 feet of the lip of the pitch. The main cave on the same day as the above film was quite drippy!
Carlswark Cavern in very wet conditions
Apologies for quality but it was my phone in an AquaPac case.