Helicopteros Marinos is a private company, not related with VII Brigade AAF. Of course, lot of civilians (and civilian companies) offered their services, often free, to the armed forces (same happened in the UK), so sometines the line is not very clear.
In the other hand 554 argentines fought with the RAF in WW2. 122 were killed in action. Many others in the Army and RN (some rugby clubs were disbanded in the early `40s, because most players were fighting for the King! And Argentina goverment was neutrao - or pro-nazi- at the time!)
As you say, one of the survivors fought in the South Atlantic War, in the "Escuadron Fenix" (Withington was Argentine) and also other British veteran, Harvey (who, I think at the time was an Argentine citizen)
Along with other missions, Fenix Sqn did this:
(A Learjet is guiding a flight of Daggers to the islands)
Regards!