They are indeed the devils work, I sweated another tonight, rear wheel dropped out & on inspection all 3 axle spacers were split and once again the "new replacements" were to large

I have a theory this may be exacerbated by the tight radii on this layout, a lot of 18" compared to double that on the previous layout. I notice the Bachmann x-6-x chassis has flanges on the center drivers whereas the Hornbys I was previously despising (due to poor pickups) are flangeless BUT also of course don't have the ridiculous axle spacers

As for replacing the chassis the space inside the body is quite narrow for most and the chassis alone typically cost as much as a whole s/h loco but food for thought.
Alternatively maybe I should maybe I should model Barry's scrapyard somewhere on the layout for all this junk to reside in!