"I've read that Butler/Wallace were Australians."

I hope you're not making that inference based on the fact that the sheet music was published in Australia.

A lot of popular music from that era was published in the UK and in Australia, even though it mostly originated in Britain.

It's just that the National Library of Australia does better job than the British Library when it comes to having complete information in its catalogue, and it often makes images of sheet music viewable online, if the material is out of copyright. That's why I always look there first.