good affordable brushes:
W7 from great for start. available small local drug-stores, synthetic but absolutely fab quality aprox 1 pound for each brush, 3,50 pound powder brush.
No7 from Boots aprox 5-7 pound.
absolutely fabulous quality & good price for the SEPHORA own brand brushes, they got 3 different price range...so it's really big choice.
Have look for Royal & Langnickel - excellent variety of brushes, different ranges, fab quality - prices starts from 1.50 pound.
Other also great brands but more expensive:
MAC, INGLOT, LAURA MARCIER, and best is SIGMA (however set of sigma brushes in tube could be even cheaper than MAC or INGLOT, and have much better quality) - however to get 'must have set' you have to prepare your wallet for huge bill...
*of course - I am not sure that all this brand are in Australia - but I hope this will helps you somehow