Hi Nicholas,
Thanks for the response. I have really good clean PDFs of the main RMSS books that I bought from ICE years ago (along with some type of Print on Demand hardback versions). The quality of the print books was not great, but the PDF quality is really good - Better than scans, in my opinion (as a gainfully employed graphic designer). It looks like they were created from the original documents.
At the time, they were labelled: 5500p.pdf (RM Standard Rules), 5520p.pdf (Arms Law), 5522p.pdf (Spell)Law), and 5540p (Creatures & Monsters).
Does that ring any bells?