Well I suppose I'm the unwilling expert.
I was flash flooded in there virtually at the bottom. We were sat at the head of the last small pitch to the final sump and a sumped crawl., not a happy experience! Basically if it's going to rain or if there is a chance of it, don't go down it. It would be very difficult to predict what amount of rain would lead to impassable flooding and of course who can accurately predict how much rain will fall.
My experience was that about a 1/4 of the cave had flooded to the roof, there are plenty of dry bits but would you want to take a chance? There is a small cascade pitch about 1/2 way as I remember, we had a ladder hanging in the stream, it was virtually unclimbable, we only got up it by a combined tactics of a climbing superman and pulling the ladder out of the stream at the bottom. We got up it with the ladder being trapped to one side from above. There may be better hangs bolted now for rope or ladder which would overcome that little problem.