I provide medical cover at MMA events. where the majority of the time there are no serious injuries, when a serious injury does occur, you need to ensure you have experienced and qualified people on scene.
we did an event last night and had Two State Registered Paramedics and Four private Ambulance Service Technicians on site. All fighters have a pre-match medical and we work closely with the referee and organisers.
as for using St John Ambulance, no disrespect but they are mainly your joe blogs worker with a first aid at work qualification. they may be dustmen during the week and first aiders on a weekend so think and think good about what cover you require.