Bevan, thank you for the suggestions and links. I had actually seen those sites before, though I hadn't realised until just now that the rail map online can be set to show historic OS background mapping, which makes in much more interesting to me. Looking at that map particularly, I can see that it could be a great deal of work just to establish the opening and closing dates for each stretch of line, quite apart from any IT issues in making the software display only the routes which were in use in a given year. Then there are issues of what constitutes closure - passenger closure, freight closure, last train movement, track lifted. I think I can see why such a map hasn't yet appeared.