Thomas coupling
The London HEMS 902 is certified for two-crew IFR and is awaiting single pilot certification from the CAA. There are 4 instrument rated pilots on type there as well.
Night HEMS operations to Primary accidents/incidents are not undertaken by air ambulances operating on an AOC, but police a/c on PAOC can. Secondary transfers (hospital to hospital) can be done by air ambulances at night subject to normal public transport landing site criteria. Flight from a primary site can be undertaken to a lit hospital site if night has fallen since landing at the site.
BungleBob
Can I suggest that landing in a 50kt x-wind by day or night with any aircraft is not recomended. A site further from the incident but into wind could save a lot of paperwork and red faces in the end.