i'm with River85 on this. it's best you contact the uni that you'd like to apply to & ask about what pre-university qualifications they accept.
generally, as far as UK pre-university qualifications are concerned, the A-Levels is highly regarded amongst the Commonwealth countries.
Aussie unis themselves do accept A-Levels, as that's my qualification going into Monash Uni. however, i can't really comment on the BTEC Advanced Cert since we don't have that sort of program in Malaysia. international students are quite a huge source of income for the Aussie unis, so most do have experienced international student offices who'll be able to help you out on academic eligibility.
another route you could consider, which the unis might suggest to you anyway if a BTEC isn't enough, is that top unis like Melbourne & Monash have their own pre-university courses/colleges (Trinity College for Melbourne & Monash College for Monash) which pretty much lead to a spot in the respective unis following graduation, provided you don't flunk the whole program, of course. it's also a more direct/hassle free route, particularly for Melbourne, since they do have intake quotas for international student applications (but it's been a while since my undergrad days, so i'm not 100% sure if they still enforce the quota).