Hi Crab
One thing to bear in mind when talking about most UK HEMS is that it is generally a VFR operation with occasional IFR recovery/diversion (Scotland being the main exception). With no PinS approaches to hospitals or HEMS bases, IFR is only much use for operations returning to HEMS bases at instrument aerodromes or very occasionally as a cloud break at an instrument aerodrome near an incident. It is very difficult for HEMS pilots to maintain approach currency unless they are based at an IFR aerodrome, so the idea of being current on military style instrument departures is highly unlikely, even if you could get approval from the Authority to conduct them.
Even for a 'proceed visually' PinS departure, you need a visual segment to the initial departure fix (IDF) and to design that, you have to have a full annex 14 style survey carried out at a cost of several thousand GBP, not a typical hospital landing site sketch conducted with a laser range finder and a magnetic compass.
Cheers
TeeS