Gautries is a high level swallet, meaning that the water level is
very dependant upon very recent rainfall (within the last hour even). With the ground as wet as it is, i wouldn't be suprised that after 2 hours of heavy rainfall it would begin to back up and soon become pretty unpleasant in parts. It seems to fill from the bottom, as well as sump in the entrance, under very heavy rainfall.
That said, with a quick check on a radar based weather site (such as
http://www.metoffice.gov.uk/weather/uk/radar/) that morning you should be able to gauge pretty well if any heavy rain is coming. Unless i saw something very scary on there i'd almost certainly go ahead with a trip. Most of the sections are close to sections of cave that don't sump (AFAIK), so just be aware as you're making your way through....