And... It's better. Perhaps I should have more patience but I have invoked the law of diminishing returns, aka the underlying flesh in my fingers is beginning to liquefy.

The drive side cone still has a minor blemish on it whilst the non-drive side cone is uniform.

Wash things out, new ball bearings, new grease then reassemble and this time things run 'smoothly' within certain definitions of 'smoothly'.

Perhaps I am my worst critic.

Now when I tighten things up to the state where they bind the binding is more uniform.

Backing off to free running with the wheel axis vertical there is no discernible horizontal movement in the axle. There is however a minor lateral movement. Hard to explain. Perhaps the grinding was not concentric or it was not concentric in its original state..

Yes, it is a damn sight better. One thing I have noticed is that the original cones appear to have vertical striations in them, or the grain structure, whereas the ones I bought by mistake suffer an annular, possibly tool inflicted, surface lines.

I've also taken the opportunity to equalise the length of axle available either side in the dropouts. Slipped the freewheel back on, silk. I think I'll have sex with myself.

Apart from the caveats about case hardening it appears to have worked. We'll see how things degrade over time.