Rather a belated response but just saw this post.
The RAF maintained a number of locomotive engines, and some lengths of track. Most of these were at Maintenance Unit bases, and were used to to transport aircraft parts, bombs and any other bulky equipment required.
If you have his service records then you can ascertain which airfields he was based at, and from there we can find more info about what type of locomotive they used. Some were very narrow gauge.
The RAF maintained some right upto the 1970s.
K
