When looking on Skyscanner for flights from Heathrow to Sydney, CSA was the lowest price.
I booked online, which took numerous attempts due to their very poor and outdated website.
Worse still, when my girlfriend came to book on the same flight shortly after, she had several failed attempts to book, and then the price almost doubled!
Generally when booking online, I had a very bad experience. At one point my girlfriend didn't even know if she had tickets or not!
Most importantly, we both got to Sydney with CSA, for a great price, and the flights weren't bad at all.
I would recommend if you have a low budget, but be prepared to have a bit of a struggle to book and navigate their website.