You're most perceptive, the light railway will have a Derwent Valley-esque feel to it, some structures will be copies and one location a direct-ish lift from the real thing. I also have in mind the Isle of Axholme, though that won't result in any physical representation. The light railway will be less of a feature than I'd originally intended when faced with the bare boards, but less is as ever more and I think that what's left will be better for it.
Earlier Ian (old dudders) suggested that I take a look again at the British Transport Film's 'This is York'. I'd last seen it about forty years ago as a teenager. Viewed again I found it more charming than I remembered and more interesting. One thing that struck me is that it appears not to use stock footage but has everything shot specifically for it; it becomes far more valuable for that. Anyway, take a look for yourselves.
I've always liked the bit where the Stationmaster says that the meeting with the union reps end up 'breathing agreement over each other'.