Thanks so much to all -- I really do appreciate it and it's all very enlightening for someone like me.
I was trying to book 2 x one-way redemptions from Australia to London. I appreciate that I'm cutting it fine timewise (we're trying to go in mid-Jan 2016, hence the need to try to have enough Avios to redeem asap, but, quite probably, I have left it far too late).
Thank you all, though, for the above replies. It's quite a community here, I'm discovering, and I genuinely appreciate all your help/comments! So thank you.