I've covered a firework event for the last 4 yrs, estimated crowd 120,000- 150,000. The casualty load is mainly determined by the wind direction!. Most years we deal with a handful of drink/drug related collapses & 1-2 medical, ie asthma, angina. If the wind blows the firework debris back over the crowd, we suddenly have 30+ casulaties with FBs in their eyes.
Staffing:     3 VAS ambulances (NHS A&E equivalent)
                 12 -15 VAS First Aiders
                2 crowd doctors
                1 Ambulance Service Liason Officer
                ~60 other first aid trained staff from local football club & leisure centre.
The key is a good risk assessment and good command & control  for the event.
Best wishes
John Apps
Basics
[Danny McGeehan] Very sensible advice John and I will bear it in mind,  BTW very nice to meet you at our meeting in Stafford and it was a very successful event
Danny McGeehan
Stafford