Well before you can book a ticket you need your visa. Either tourist visa or if you want to work out there a WHV (working holiday Visa) which is if i understand correctly valid for 12 months from day of entry to Oz (but you can only stay in a job for a max. of 3 months then must move on). To get one you need £2000 in the bank and proof of this.
Once you get it book your flight & go!
As the legend that is Peter Kay says "Booked it, Packed it, f***ed off"!
p.s. if you delete any confirmation email for someting you have bought online 99.9% of companies provide a customer contact phone number on their site. Give them a call!