The National Archives at Kew will have the official correspondence from the commander at Gibraltar to the CinC, Secretary at War etc. I've just had a quick look at the courts martial register and there were two privates of the 1st Foot tried for mutiny at Gibraltar in March 1803. The only ones I can see for the 54th are for desertion and sodomy! Not many of the trial papers for other ranks survive though.

Regards

Rob