You are indeed correct flyinggit aircraft subjected to unlawful intereference are the HIGHEST priority, followed by:
-Multi-engine aircraft that has lost an engine.
-Aircraft with radio failure.
-An aircraft which has declared a 'Mercy Flight'.
-Aircraft involved in SAR, 'Med 1' or under a 'Hospital' callsign.
-An aircraft operating under a 'Polair' callsign.
-Heads of State.
Then...
You lot in your big shiny jets!
Source : AIP ENR 10.1