Well I did say feel free to correct any errors, but I think the main premise is valid; so I thought it would be worth following up, as I would like to know the truth of it. Here's what I found so far:
Extract from Wikipedia: "Legend has it that there were just three aircraft, nicknamed 'Faith', 'Hope' and 'Charity' but, in reality, at least six Gladiators were deployed."
Extract from website of the UK Maltese Cultural Movement: "Talking to people in Malta who remembered those dark days of 1941 when the Church of St Publius received a direct hit that destroyed a large part of the building, and how they remembered the valiant efforts of the three aircraft and their pilots in trying to defend the island."
Extract from the Oxford Companion to World War Two: "Faith, Hope, and Charity were the nicknames of three British Gloster Gladiators, obsolescent biplane fighters. At the start of the siege of Malta in June 1940 they were the only air cover the island had. Originally there were four, found in crates aboard the carrier Glorious, but one was destroyed almost immediately."
Extract from Amazon.com description of the book 'Faith, Hope and Charity' : "Faith, Hope and Charity is a story of three Gladiator biplanes flown by six volunteers from their base on Malta and fighting alone against the Italian ‘Regia Aeronautica’ between June and October 1940."
And I just found this movie (1 hour) named - you guessed it - 'Faith, Hope and Charity'
http://video.google.com/videoplay?docid=205252973949369270#It's a slightly amaturish animated tribute (but after viewing 15 minutes or so I'd recommend it) which claims that they had more Gladiators but were never able to field more than three at any one time. Whatever the truth, I don't think it diminishes the legend even a little bit.
Thanks for pointing out the discrepancy WM, seems like there might be more to uncover there. I'm going to finish watching the movie. Salute.