About time I put this one to rest. The answer behind this puzzle is that the generator was there. Past tense! I just didn’t know what the guts of one looked like. I didn’t understand that there are the remains in the photo, and I had been put off the scent by the state of the Rotol gearbox fitted to Camden Museum’s A79-14. This gearbox has a blanking plate over the generator position and the Dunlop pressure reducing valve (AHO19682 – for the Canopy Seal line) and its mounting bracket (L002109A) attached on the blanking plate, as if the blanking plate should be there for a serviceable aircraft. (Although I would certainly mount the bracket over the blanking plate if I had just removed the generator – to keep it all together.)
Below is the image from AP.1095C Vol.1, Sect. 5, Chap.9, that made me see the light. Notice the long bolts that run much of the length of the generator, holding the casing and mounting together. This is actually for the KX, but is much the same for the KX-B.