Thanks, all. Can't say I agree with John's assessment of Chandon, which I've sampled a fair bit of in UK and Australia. The Argentinian version is quite different - less complex, more fizz, and considerably sweeter. I might've been a dud batch, but it tasted a lot like the other couple of domestic sparklings I've tried, which makes me think it's made with local palates in mind.
That said, any sparkling I bought in Aus/NZ for $8 would be...actually, I don't even want to think about it.