I didn't think about it from an insurance perspective, I'll check it out. They produce pro Muay Thai and MMA fighters, so i'd imagine the gym has some sort of coverage.
Insurance and legal cover is the most usual; reason for using these organisations, many don't interfere with the style or what you are teaching. The gym should have insurance not just for the martial arts training but in case you hurt yourself due to their negligence in something like building maintenance, or employee's being negligent etc. it may sound excessive but most people can't afford to be off work for any length of time due to injuries either from training or accidents.
Which gym is it, if I can be nosy, I know most people in MMA in the UK