The attached link leads you to the report of their AGM in November. There are two documents worth reading.

https://sites.google.com/view/serug/publications

One is the presentation given by Nick Hurrell, their Secretary, at the 2024 AGM.  It outlines recent performance on the line and how it might be improved. It shows where infrastructure upgrades might be effected. It also shows the considerable growth in passenger numbers compared to pre-Covid times.

Second is the presentation given by Neil Drury at the 2024 AGM.  It describes the plan to replace the class 159 units with a fleet of hybrid third rail and battery units.

This has also been covered by the Green Signals podcast on YouTube
https://youtu.be/J--7a2wy0wM?si=tNsI9BVaazXeTCis