A great deal of Network Rail documentation is covered by Government processes for information classification, and anything marked as “Official” cannot be distributed outside the organisation without permission.
As a Signalling Tech, I have access to pretty much all signalling diagrams, but if it were found out that I had distributed all or any part of them to outside parties, I would face disciplinary action. Most of what is on them is either meaningless to someone without training, or no more than can be gleaned by staring out the window of a slow moving train, but that’s the nature of any schematic really.
Where I maintain a local copy (for when I go out of mobile signal areas, easily done on my patch), it must be on a Network Rail secured device, and where stored in the Cloud, it must be on the one service approved by the company. Even sharing of docs among staff has to be done via our Teams service, cloud sharing, or internal email. WhatsApp (and its ilk) is very much banned, which often makes me wonder why some other public sector employees (!?!?!) get away with using it.
As someone mentioned before, the 5 mile diagrams were useful, but these days don’t seem to be well maintained, and are covered by copyright as they were produced by an outside party. We also use simplified TAP drawings for maintenance, but those are also produced externally and are copyright controlled.
My reference points are mainly the Sectional Appendix (freely available, but not of use to your purpose), and M12 diagrams, which show an overview of all signalling equipment in an interlocking area and where to find the associated location cases. M12s (and the slightly simpler M1s, which just show the layout of equipment on the track, but without the location case data) would probably be what you are after, but as I say, anyone found to be distributing them would be in serious hot water, and there are thousands of them (one for every single interlocking in the country).
There is no single central repository or atlas of signals and their locations.