Ok, finally got there. The CSO ('Jacqueline') had no idea what I was asking for, but she did note that she was just back from LSL! After initially saying it couldn't be done, she then looked up the instructions. She still couldn't work it out so had to consult someone more senior. We eventually worked through it together once Jacqueline got what I was trying to do and stopped trying to offer me a Classic Award. She did try to charge a booking fee but I said 'Qantas has advised there should be no booking fee'. She seemed a bit dubious that this couldn't be booked online but I think in the end she believed me, because why would I be going through all that hassle if I could have done it myself! Jacqueline tried very hard to be helpful even though she was just working it out as she went along, and we had a laugh in the end. She asked if any of the other CSOs seemed to know how to do this and I said I'd heard they didn't. She warned not to be upset if they get a bit cranky when we ask for these bookings and they don't know what to do! I said it wasn't their fault that Qantas had changed the system and not trained them to deal with the consequences.
Anyhoo, got the flights I wanted for the right number of points and just a bit more co-pay than I expected. Thanks guys for your help. It will be worth it if I can crack WP