Another attempt today: I replaced the internal bearing ring and packed it with grease. All was well until I mounted the wheel and I found that, just as you said, it is incredibly easy to tighten the bearings too much and /or put too much pressure on the hub when tightening the axle screw, so thanks for the tip.
This is a problem: at the moment the freewheel works, but the cones have what seems to me like too much play in them; I can rock the wheel back and forth. However, if I tighten the cone by a quarter, the freewheel stops working.
Is there a way to find a sweet spot, or is a wobbly wheel normal?
I had exactly the same issue on the Orange Brompton I recently restored, in the end I settled for a tiny bit of play in the hub, over tightened bearings just don’t sit right with me.