Changing countries for your Billing address is apparently something that Microsoft Billing can't handle. If you used a the same LiveID for your new subscription, your old subscription would have to have been canceled. Each LiveID can only have a single active OneCare subscription associated with it.
When you sign in at http://billing.microsoft.com do you see one active and one canceled subscription (never mind the language settings...)?
Did you use a different LiveID for the new subscription? If so, then the old one may still be active. Each subscription would be associated with a LiveID and signing in at the Billing site will show you the status of the subscription for that LiveID.
Now, as for the language setting. Delete your cookies and temporary Internet files in IE and make sure that the default language is shown to be English-AU. Log back into the Billing site and it should be in English - I hope.
-steve