Rowan,
I don't think I've ever said "hooroo". I assume it means something like bye-bye: is it an Aussie expression?

That it is, Snuffy.
It was more frequently heard in my youth, along with such terms as cobber and bonzer (both of which I think I've seen in Mudcat's Oz glossary) but it is still heard occasionally among older people. There are other Oz terms meaning bye-bye that still have currrency;
"Bo-bo" is heard among indigenous people in the Top End,
"Catch yah" is heard more in rural areas than in cosmopolitan ones,
and "Look after yourself" is widespread.

Apologies for the thread drift but I reckon there's some relevance to the song.

Cheers, Rowan