Once you start looking you start seeing. I've been to the Local Studies Centre at Manchester Central Reference Library hundreds of times but have yet to look for Manchester & Salford Co-op material. I've always been researching other matters. Checked the excellent National Archives website and it appears there are 142 boxes of material hidden away in that wonderful round building.
National Archive : List of boxes
This picture was taken in 2005 of an artist painting the library. It was shirt sleeve weather.