HEMS in UK cannot 'self task'. Task has to come from (or be approved by, if HEMS crew happen upon an incident) an NHS ambulance control.
Upset 'control' by refusing a task ...then watch the helicopter call out rate drop for the rest of the month!
I observed 12 years of this. Hopefully with the increase in doctors on HEMS crews, Amb control managers' histrionics will finally be nipped.