I found this on YouTube, VisaFirst.com, I know you said to only use the one you linked to, but VisaFirst provide:
Visas Very easy to do yourself online, using the link in post #1
A bank account Also very easy to do, for free - you can even set one up before you leave the UK
TFN Also very easy to do yourself (for free), online, once you're in the country
Airport pick up Depending on which airport you're flying into - Sydney is the most common one, and the only one I've ever flown into internationally, then there are several ways to get into the town centre. In Sydney, you have the option of the tube ($15), taxi, or some hostels offer a free pick up service - Nomads Westend does for instance.
accommodation Very easy to sort it out yourself before you get there by going on hostelbookers / hostelworld
job assisstance Despite having come across several of these job assistance things, I've never found them to be much good. Look at some Australian sites for guidance on a CV, Aussie-style. Get a friend to proofread it, and then go out and be proactive. The two services that spring to mine - one did little more than check your CV ("it's fine" they said to me, and that was it), and the other only did farm-based jobs.
free interenet Useful, to some extent. However, if you take your own laptop then you can always use McDonald's wifi, and I'm willing to bet that you will only be able to get this free internet when you are inside their office during their opening hours. Not only will you not always be in the right city, but the office may very well be a pain to get to.
travel discounts Usually a pile of self-serving tosh that works out more expense for you.
They seem quite good, would you recommend them? How much are they charging you, and how many night's accommodation does it include?
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I'm thinking of going inbetween the second and third year of my university course. What is the weather there like in June-August time? I know it would be their winter, but is it as bad as we get here in the UK?
If you're in the temperate southern half, then it will feel a lot like a UK summer. If you're in the tropical north, then it will be the wet season (don't go there in wet season!)
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Do I need $5000 on a work visa, even if i have work liked up through the likes of helpx.net or workaway.info
Theoretically they could put you on the next flight home if they discover you have <$5000, so it's always preferable to have it. In addition, the vast majority of jobs on helpx.net or workaway.info are just work for food & accommodation, rather than actual pay. That just means that it will help keep the wolf from the door a little longer, rather than increasing your bank account.
$5000 is enough to support you on a modest backpacker lifestyle for about 4 months, but after that you'd be penniless, wouldn't have gone anywhere and wouldn't have seen anything. General rule is to take as much money as you can, and always keep a close eye on your bank balance, making tough choices if need be.