All good advice.
DFM's were for non commissioned "men"; the DFC was for hofficers. On gaining a Commission, his Service Number was changed (as previously explained) therefore if anyone has his medals they may not think they are for the same man. The DFM was a fairly rare medal (not just issued willy nilly "with the rations") and to go on and gain a DFC is rarer still. Well worth investigating further and I am sure the London Gazette citations will only be a fraction of the story.
If you know his Sqdn, there may be an Association that can provide additional information. There are Operation Record Books detailing what was done by the Squadron.
If you know the wartime address of his parents etc, then there may be local newspaper archives in the Local History section of the library. If you can't get there, the librarians are usually helpful or may be able to suggest some researchers for you to contact.
There are plenty of books too, so Google a Search to see what you can readily find.
Don't forget to keep us in the loop, especially if you come up with original memoirs and stories..