There must be some way to contact the universitys and discuss your situation. I wouldn't think a 1/2 or whole A level makes a huge world of difference. Be adamant that you have the right courses and haven't really missed out on alot.
Depending where you are; you should be able to apply for some work experience. Find someone who knows someone and ask them if they can sort you out for a day. Unfortunately with science jobs you will not be allowed to do any lab based wok due to training, safety and most probably IP. Just go in for a day if you can and have a look around talk to people and make sure you find out what they have been doing.
Yeap; you need a gap year to bore people to death in fresher week about your time in Australia.