Ta for that.
I went through the "missing points" link and tried to claim my missing points. Nup - already allocated according to DJ...
Hmmm.
Unless they're doing something sneaky that I'm not aware of, a $~240 fare should produce ~1400points. In my case it's been around 600 produced so far (which sounds like the correct points for my outbound trip) and no more.
Oh well. Have lodged a query, and will find out sometime soon what the real story is...