Whilst some shops (M&S) have some quality issues, it's not so much a matter of price and needing to buy a very expensive bra. You can get some fabulous bras at very reasonable prices - admittedly I can't tell you the Australian sources but over here (and they do international delivery) look at www.brastop.co.uk for an idea.
Now, the most likely reason for the 32B feeling too tight is that it was too small in the cup for you. If the cup isn't big enough, then it pulls on the fabric in the back making it feel too tight. So I am around a 30HH, but I can't fasten some of my old 30Gs at all and my 30GGs are unbearably tight.
The easiest way to do it is to go and pick up a 30C/D/DD/E (always better to try a few bigger too as it's easier to spot a cup which is too big than one which is too small) then pop the bra on back to front. It should be fastened on the loosest hook (one nearest the end). The reason for trying it back to front is to isolate the band from the cups so you can check the band is ok. It should feel firm (and will feel tighter than your 34s obviously) but it shouldn't be unbearably tight. If it's awful then you might want to try a 32 in that specific bra but given that you measure 30 I would suggest until you are very sure of your size that with each new bra a 30 is your starting point.
Once you are ok with the back, pop the bra off and put it on. To do this, put your arms through the straps, lean right forward and drops your boobs in to the cups.
Now time to scoop. Reach round and fasten the clips and stand up. All those bumps, lumps, back fat, armpit fat - they get yanked in to the bra! However it only works if A: the back is small enough and b: the cup is big enough. Until you are used to it, stand side on to a mirror. Lean forward, put your right hand inside your left cup, reach round as far as you can and pull/scoop/yank all the flesh/soft tissue that is bumping under or over the back, around the straps or the armpit and haul its ass in to the cup. Repeat at other side. You might need to do it a couple of times (as doing one side knocks the other out slightly)
Now have a look and see how the bra fits. A too small cup will have bulging somewhere - not necessarily in the middle. Depending in your shape you might bulge between the cups, over them, at the armpit or towards the back. If the cup is too small the scoop won't have the desired impact. So any bulging in these areas try a cup size up first.
Australian sizes - according to a couple of websites I have just checked, a 30 is an 8 and the cup sizes are the same. Are you sure a 34A is a 10A - if these charts are right then it would explain why trying an 8B was far too tight as the cups would have been quite a bit smaller than you need.