im sorry i am also in australia so i cant reccomend any schools but here is my 2c
when you get down to it although they are both jobs that require you to create things, and allow you to use creativity to design on a daily basis fashion design and architecture are very different jobs in very different industries.
Id say work experience is the way to go, suss out what industry you enjoy more. I like the sound of the architect in New York! It sounds like an amazing opportunity...Architecture can offer more stable jobs, and you can also pursue your interest in fashion on the side, if one day you make the right connections you can start making/ selling your own clothes or maybe collaborate with someone - have fun!
and remember if tom ford did it....