Ex- UK .....Thomsonfly
By far the cheapest but also not the best. Last year it was a 767-200 with about 270(ish) seats by memory. Via the middle east and singapore to Sydney. A friend paid about 300 quid return.
Personally I always go Austrian (ex Lauda) on the 777, it is by far the quickest (and well priced) way from europe to Oz, pretty comfy and cart tarts aren't to bad on the eye
If you have dates now, then book now dont wait.