In case anybody is interested I have posted a scan of the 1964 Gloucester to Swindon timetable on Flickr, illustrated with a photograph of one of the Chalford auto trains
https://www.flickr.com/photos/93122458@N08/50192933291/This was of course the last timetable in which the intermediate stations were open. From 2nd November 1964 only Stonehouse, Stroud and Kemble were left as intermediate stations on the line.