The need to defer not only depends on your financial situation, but also on what you've done in the void between uni and the end of the hsc. If you've worked your arse off, will be living at home and still have a few hundred saved up after enrolment/textbooks/getting trashed with a steady flow of income, a year off just to save more money isn't necessary, unless you want to qualify for independence or want to travel far, wide and reasonably comfortably.
Personally, I think I've managed to squeeze in a lot of the 'gap year' stuff into the four-month post hsc void. I've worked my arse off for the past two months, working 5 6 days a week whilst depriving myself of 'fun', and do believe I've developed a lot more maturity than some others who've been pissing it up night in night out on their parents' money. In that time, I've also had a taste of the mind-numbing monotonity and isolation from friends and family that comes with such a routine, so the aforementioned group have enjoyed the past few months a lot more than I have and it definitely has been a struggle, the 35-40 hour week (the job wasn't the greatest either, working as a carnie at Luna Park). But in the end it was worth it - this Wednesday I'm off on my own for a month around South East Asia, all expenses paid by moi (or most of it anyway), from passports to airfares and accomodation, it was something I really wanted to do (I didn't go to Schoolies), so yeah.
I know a couple of people who are going on a gap year - one of them is also going to England on a 6month working holiday. If you want a compromise, study part time so you can work a bit more. That way you'll earn and save more while making progress towards graduation and subsequently, your ideal career. It's what I might do upon my return should I get a proper job in the public service.