Rottweiler - look no further than the Defence Helicopter Flying School at Shawbury to see civilians (no licence required) flying contractor owned, military registered (dual in fact I think) and operated aircraft to military rules and regs, including NVG.
The problem with the Air Ambulance setup is that it is parochial by nature and, whilst limited cross-border ops are not unusual, I don't believe a National response is possible under the present command and control structure (local assets for local people
)