Robin,
I've found an electronic copy of a classroom manual/booklet for the US 1/8th scale Model of the M2 Bailey Type bridge. This booklet shows the instructor how to set up the class to teach students how to assemble the model. It also gives a list of what the whole model contains and how many crates. Interesting stuff. I suspect you'll have a greater opportunity to find the US version than the British version and if you do it should go well with the treadway rafts!
Here's a link to a site where somoen is showing his M2
http://ssccdispatches.yuku.com/topic/274/Bailey-Bridge
And a video
http://www.youtube.com/watch?v=PYjDujkq-uc