A little while ago I put together a document with links to many parts of the website where there are materials which I would regard as archives. I mentioned this in one of my archive pieces in the journal, https://britastro.org/jbaa/pdf_cut/jbaa_26268.pdf
This is the document https://britastro.org/system/files/BAA%20Archives_1.pdf
The digitization of our archives, with them then being made available to members, is something I have been working for since becoming archivist. As an example of this I uploaded all the handbooks back to 1922 some time ago, after Sheridan sent them to me. I do not have the circular scans but it would be a simple matter to upload them once I do have, plus the other material mentioned.
There is much more that could, and should, be done. Most sections have archive material. Some, but definitely not all, is online. These section archives are not within my control.