You are right, Peter. My CAT manuals were produced by Pye at their Oulton works in Lowestoft and are dated 1956 and 1957.
Tony,
I don't know how detailed your research is but it might be worth asking your original question on PYE "Outworking" sites on the WW2Talk forum. There will most likely be a list of the small production locations in The National Archive and you'll find several people on that forum who provide TNA file searches and copying for third parties. I've used ARCRE for this purpose and was happy with his service.
https://www.arcre.com/
73
Roger/G3VKM