http://www.instructables.com/id/WWI-Trench-Model/?ALLSTEPS
Seems good, bugger that you need a glue gun, but dad regularly goes to screw fix and they have them cheap so....
Anyway, it seems to work I've messages the guy but I'm not that sure he does it anymore....
And so, time to start a separate money box funds, named (originally) "Airfix/diorama funds."