Am doing an international - domestic transfer in SYD (arrival 7:30am on a Sunday). And wondering how much time I should plan for given I will be on two separate PNRs, have to collect a bag, immigration/customs, take the shuttle between terminals and recheck my bag, etc. I am thinking to hedge my bets three hours.

That aside, if I were to book a flight at the three hour mark but things go smoothly and only take a couple of hours would Virgin allow me take an earlier flight without additional cost or require the change fee? The same question if things go belly up and I arrive late how are they on putting some on the next available flight? Virgin has almost hourly flights through 1pm so trying to hedge my bets given I will be on two PNRs.