Robin, thanks for the reminder about the Maskol trick. Haven't tried it myself yet as I've been modelling a period that didn't much need that sort of thing. But for my forties layout I will give it a try to some limited degree.
Tim, thanks for the info. Interesting that the keys are oak, didn't know that. I'm not going to model rotten track keys, that was just a general interest question. You raise a good point though: Some of the details recorded above would simply not be visible in 4mm, and modelling them might have the opposite effect of realism. So that's one conclusion from this little exercise. But I'd like to capture some of the other details, like the newly replaced boards, and the way the stock weathers. Nothing new in that of course, but it's nice to have observed these things for yourself before replicating them.
Ian, yes it was a bit heretic not to visit Pendon, but I didn't even have time to see all of Didcot either. I remember seeing a photo of those cobwebs in the barn though. Made from tissue, eh? Did they stretch it? I had no idea you are also at Didcot! So I missed both you and Castle. Argh.