As Jetscream says, JRCALC guidance has been issued. My partner is a HEMS doc and as the document states they are doing no transfer/retrieval of incidents where Covid19 is suspected, they are going instead by road.
She is also of the impression that her HEMS service will go offline in days. There are is less RTC related trauma at present due to the associated lockdown, furthermore ED and Anaesthetics consultants are in demand at the minute in a hospital setting.