Thanks everyone.
I think that progress on this will slow down for a while. The wheel-making experiment didn't turn out too well, so I've got to look at some other way of making wheels and tyres for this. Also, propellers are going to be a problem - all the props in my spares box are for fighters and are thus too small. I'd like to make the props from scratch, using wood, but really haven't a clue how to do this.
The next thing to do will be to make the struts, which will be quite tedious. I've also given thought to the engines. I have an unbuilt Roden F2B and the engine from an already built F2B. Although these are Rolls Royce Eagles, and the DH10 used Liberty engines, they're both V12 engines and I really don't think anyone could tell the difference in this scale.