Sicily was famous for being brigand-infested (and was largely under British control, though Ferdinand remained king). (As it is today, if you replace "brigand" with "mafia.") So I don't think one can assume that his death was necessarily the result of some nefarious scheme by Britain's enemies. In fact the British directly or indirectly encouraged both brigands and privateers, sending them to southern Italy to harass the French, so it might have been a case of "blowback." The problem with arming thieves and assassins to act as guerillas is that they are thieves and assassins first and foremost.