Thanks all for the replies.
The fact the conservatives are against it (and Labour fence sitting) is the best argument for it

I can't believe they're running the 'it's too difficult' line. The prefect comeback to that is do you think you're dumber than an Aussie

(the pro-camp should've used that

)
But as you say Cricky & Wooster - it's often used in many other countries, states and regions besides Australia. I understand they call it Instant Runnoff Voting in the US where it was invented and used in several states and counties there, probably by more people than there are Australians.
(I have a hypothesis as to why the Aussies took it up. I only have circumstantial evidence to back it up, and then old, but it panders to my prejudices

. Australian Labor and unions >1890 were the most organised labour/union in the world then and stayed strong for many decades, politically united. There was only one party representing the workers, and the right, the parties for the bunyip aristocracies, big businesses and other wealth were splintered over a 1/2 dozen or more at that time. Hence the conservatives needed AV or it would've been Labor every time, and it's conservative interests that always write constitutions. My theory goes to shit lately though. Our conservatives lost the last federal election that they would've won convincingly on FPTP, but still support our form of AV. Tasmania and Australian Capital Territory (my joint) adopted a variation of STV known as Hare-Clarke and it favours progressives more than not.
My biggest surprise was NZ. I had always maintained that big parties would never surrender their privilege for a more representative system. Then NZ Labour and Conservatives in a bi-partisan throat cutting for the betterment of the nation brought in a representative preferential system and I was happily proven wrong. (I've no idea if it's an STV variant or what - looking it
http://en.wikipedia.org/wiki/Sainte-Lagu%C3%AB_method - anyway, I didn't follow the half of that

but apparently it's really really fair
http://en.wikipedia.org/wiki/Gallagher_Index and it can't be too hard 'cause Kiwis use it

Sadly, my cynicism doesn't look to be proven wrong though for the UK. I looked up the betting odds comparisons and pro is paying 6 to 1 and anti is virtually money back.