Now I can start plonking things in position to get a feel for the model. The main feature is the road so this is cut from 3mm thick MDF. I know people are funny about MDF, but it's flat, stable and if thin enough (like this) can be cut with a heavy knife, albeit with many cuts.
Where the road crosses the canal, it's propped up on a couple of sanding blocks which give a pretty close approximation of the 6ft clearances on the real thing - I had to stoop to walk underneath.
The track is supported 75mm above the road on foamboard T-shapes for the moment but I'll do something more solid later.
I've lived with this for a few days, and shown it to Jason and we are both happy. The position of road, rail and canal have changed from real life, which will need to imaginative work later, but it all fits and looks nice IMHO. And if it doesn't well, it's too late as I've glued everything down by the time you read this.