Locally the timetable was known. I still have a copy of the emergency timetable dated 21 October 2000.
I also have an undated one page of A5, which I think must have been from the day after the derailment, and looked roughly like this:
Services to and from London Kings Cross
Cambridge to Kings Cross
xx:24 and xx:54 past each hour
Kings Cross to Cambridge
xx:06 and xx:36 past each hour
Approximate journey time 1 and a half hours
Last train from Cambridge 23:24
Last train from kings Cross 00:06
There was also a manuscript addition:
On the hour shuttle last 23:24
I think that means on the hour Cambridge-Royston with the 23:24 up being a 4 car train and stopping at the villages.