In case it helps anyone else, I went to the Artesia site, switched to French, selected the www.voyages-sncf.com option (on the left, under Réservez) and put in the rest of the trip details (fairly easy to figure out the form, even for a French novice like me). That transferred me to www.voyages-sncf.com (still in French at this point), where I needed to add more details, and I selected 'Australie' in the country list at the bottom. I was then redirected to www.tgv-europe.com - in English! From there I just followed the prompts, and even had an option for free postage of the tickets to Australia, so I don't have to muck around with retrieving the tickets from a machine in Paris.
You may be able to shortcut this by going straight to the TGV Europe site, but this way worked for me, and I saved nearly $150!
|Artesia Palatino - day|
|Artesia Palatino - night|