The Falklands was the last major battle and the Marines would be best suited to the isis predicament the SAS /SBS are more secretive in what they do they don't do large scale only intel and important individuals
Yes your right, Ark Royal was the last and I have no idea why illustrious is the last one left the only reason I can think of is that it is the preferred ship by the admiralty and naval staff as a active member I've never heard a bad thing said about "Lusty"