Just rang the friendly UA contact listed for Sydney (131777). Immediate answer from their ICC. I said "I have confirmed flights on xx April SEA-NRT-BKK in Business and I'd like to use my points to upgrade to First class". He said (after noises of a keyboard being pounded) "yes Sir, I can confirm your First class seats on both these flights - it will cost you 30,000 UA miles...(and so on).

A refreshing change to the QF lottery.