Just a quick update on the diorama, as I've now scribbed the stonework on the right-hand bridge support and cut the rails to length.
The rocks were scribbed into the plaster using a dental pick, which worked nicely. The pattern isn't fully accurate to the actual bridge but I think it should work reasonably well once painted up and part hidden under plants.
The ends of the rails are likely to be hidden where the track is over grown so I've soldered them to copperclad PCB strip for strength rather than relying on the hand spiked sleepers to hold everything in place. This should also make fitting the sleepers easier as the gauge is already set.
While neither of these tasks are huge in themselves, I do feel that the scene is starting to come together nicely now. I see I still have a bit of work to do where the girders join the left bank (that gap needs filling) before I start painting the rocks, but I can now also crack on with building the track and detailing the girders and those jobs should move the diorama forward quite quickly.