Part of the problem is possibly that in the UK, police & air ambulance a/c are civilian, and have to be operated to Cat A most of the time.
Absolutely not true for HEMS. Think you need to reread "Appendix 1 to JAR-OPS 3.005(d) - HEMS", and "Appendix 1 to JAR-OPS 2.005(h) - HHO".
As has been pointed out many times before; the helicopter is certificated to Category A and operated to Performance Classes 1, 2 or 3. In the case of the 'HEMS Operating Site' the
standard is PC2 with Exposure and the regulations are being amended to say precisely that.
Jim