You are 100% correct about the 'airspace' ownership.
But, regardless of who owns what - the creation of 'a nuisance' inflicted on the lowly earthlings below is indefensible. Unless, of course, they moved into the area after the airport and navaid were commissioned and their Titles were amended to include this risk of noise nuisance.
Instead of heaping it onto the Busselton owners, maybe some of you should ask them for specific details.
happy days,