Probably most important is what it is worth to you

Any benefit of time in the lounge may well be rather undone by the long Y flights. £400 plus buys a lot of good meals in Oz - I might be inclined to find a quiet corner of a bar in the airport , spend £20 on drink and snacks of my choice and enjoy the balance in Oz.

Priority Pass or similar paid lounge access might be worth considering? (And cost less than £400+)