I've mentioned before the two Prime Ministers of Australia who have identified as Cornish, Bob Hawke and Robert Menzies (Probably the two most iconic PMs you're ever likely to find). However there are many more heads of Australian government either actually born in the Cornish homeland (Kernow in the Cornish language) or else born into a Cornish Australian family.
George Pearce was acting prime minister for seven months in 1916 while Billy Hughes was overseas and remains the only Senator to have fulfilled the role of Prime Minister without resigning his Senate seat.
Premiers of South Australia
George Marsden Waterhouse
James Penn Boucaut
(please tell me if you know of any more)
Premiers of Western Australia
John Trezise Tonkin
Premiers of Tasmania
Premiers of Queensland
Premiers of Victoria
Note should also be made of John Langdon Parsons who was Government Resident of the Northern Territory.