Fairly sure I've got something basic wrong here, so I'll describe what I di d.
I sanded back (sanding with the grain) the damaged patches with 80, then 12 0, then 180 grit, and wiped all dust off.
I then oiled with a rag and Liberon Superior Danish.
In some places the oil took nicely, as expected. In others, it was immediat ely obvious that there was a problem. The surface remained matt, almost gre yish - in the worst places it looked as though the oil was mixed with dust. Now it has dried, all these matt patches are still matt, still look like t hey have much less oil on them, and look pretty poor when the sun shines at the wrong angle.
Thoughts? Found one suggestion that I should use white spirit (or meths?) t o ensure all the dust was removed, but this doesn't seemed to be mentioned on any of the guides to oiling worktops that I've looked at.
