Thanks all for a fantastic response - there are some great leads here and I shall enjoy investigating them all.
WHBM and JENKINS - Thanks for some really interesting thoughts. In principle I support what you're pointing out in that a pilot's memoir won't have much to do with the social and cultural aspects of the Empire. What I'm more interested in is whether from analysis of the writing we can conclude anything on how the pilots themselves considered their position - can we identity any subtextual references to some sense of Imperial duty? Can we deride what their attitudes towards the people and places they were flying to were, and if so what does that tell us about the men of the operation? Conversely, if we can't find this does that tell us that by the time period the collective Imperial sense was found lacking, even amongst the men most intimately involved in connecting the Empire?
I may very well be on a wild goose chase here, but I'm rather keen, after reading endless histories that never seem to escape government records and reports, to attempt to add a human factor to my research. We shall see what turns up!
I agree that passenger lists and the relationship between passenger and cargo payload is interesting. Indeed, the fact that IA was mainly used by government officials to travel between the dominions, and not run as a commercially viable passenger service, tells us something of its perceived importance to the 1930s Empire and its Government.
On post, its significance is undeniable - one only has to look at the BA fleet today and still see the RM crest flying! The Empire Air Mail Scheme has featured rather heavily in my work thus far.
Many thanks to all the kind people with suggestions and comments, you are a testament to your community!