Thanks apx068. Concentrating on UA, then QF and CO (in that order) sounds like a good idea. The advantage of UA will also be the fact that my wife will be a UA elite next year.
But are you sure that UA gives miles on deep-discounted tickets? A travel agent told me otherwise earlier this year, just as I was about to buy a UA ticket (I think in H class). So I went with CO instead. (I'm off on Wednesday.)
As a result, I just need a quick mileage run to get the 3,000 miles I need for elite myself next year...
Jon