I've only been the once but I met three kinds of people underground in the cats.
French cave'ists - caterphiles
British cave'ists- tourists
Grans, daughters and granddaughters. All in pink wellies taking a Sunday morning stroll
There are rumors of police underground, but providing you use the correct rituals; running from people walking their dogs and sitting silently in a darkened passage for 15 minutes praying to the gods of the underworld, you don't meet these appertains
The biggest problem is trying to see everything in one visit thus leaving you aching and blistered. Better to see 80% and enjoy every minute.