For those who haven't seen my lengthier post-visit email, here are my main observations, as requested:
My aim was to look at maps, railway-,related documents and any images that would help me to understand the development of the branch and Smallford Station, in particular in its latter days.
I managed to see a number of relevant maps and documents which related to them, and Jon Musk kindly helped with photography of the large-scale OS maps most pertinent to my aims; I look forward to seeing copies of the 'targeted' photos in particular, in due course.
Reassuringly, I learnt that I had not been led astray by any of the relevant material I had previously seen elsewhere, and that there was also a lot of interesting 'background' info in the Archives, to 'explain' developments more fully.
What I plan to do next is progress my developing ideas about the station area around the late 50's/early 60's, if possible with more input from folk who have relevant memories of it, and possibly also the earlier history of Wilkins Green Terrace.
I'd like to visit HALS again, to ensure there's nothing else of importance to my researches in the Local Studies Book collection (which I only had time to look at very selectively), in terms of images mostly, and will probably wait for a further group visit to be arranged to do this.