A good start would be P.E. Abbott and J.M.A. Tamplin, British Gallantry Awards (Nimrod Press, London, 1981).** Also Medals Yearbook produced annually by Spink.** See also Nick and Carol Carter, The Distinguished Flying Cross and How it Was Won (Savanah Press) and Ian Tavender, The Distinguished Flying Medal Register for the Second World War (also published by Savanah).** And though not British, the following website may help:
http://www.airforce.ca/citations/index.htm