In my quest for information on the Tongham branch line I discovered this website:  This resource is invaluable in locating the original parts of the line that have now been demolished, it allows you to point at a location on one map and see a crosshair on the other, it is also possible to swap maps for different issues of OS map. In the screen grab above I have the OS 25inch, 1892 – 1914 Map selected on the left and the current Bing satellite map on the right.

An initial glance is showing that Tongham Station has been redeveloped:

And that there may still be traces of the Ash Green station, it looks from the new map as if the old station building is still there the track is still there though I know the rails have been removed and the bridge is still intact: