I know--and love--both those books.
If you'd like to see the visuals for the original Oxford-Cambridge expedition (the Tim Slessor book), the original film footage has been issued on DVD: http://www.teeafit.co.uk/firstoverland/index.htm
There is also a program the BBC commissioned for the 50th Anniversary called "Time Shift: The Lost Road - London to Singapore." It features David Attenborough as presenter, and interviews with the five surviving expedition members. (It's floating around the internet on the BitTorrent sites and not too difficult to track down, if you do that sort of thing.)