Phil,
Yes indeed, have been trawling any information I can come across, it's surprising how much is out there. But, I think I'll have problems finding details for other railway buildings.
Looking at the working timetable, it was interesting to see a couple of freight trains to "Elson Sidings" but I've had difficulty working out exactly where they were. Looking at the 25 inch map my money is on what seems to be an industrial building on the Welshpool line just around what looks like an abandoned triangle. As a local, is this right and do you know what was produced there? Looking at current Google maps the buildings seem to be in process of reclamation by nature. It'll give me some idea of the sort of freight traffic one would have expected to see.
Paul