While the game is the same, the DRM that locks regions is causing your PS4 to think they are different. Note that any physical disk whatever the region will play in any PS4 from any region. However, they are incompatible as far as the PS4 is concerned. Since your game is UK (aka Region 2), it is not compatible with Australia (aka Region 4): thus no save game transfer.
Since you mention the DLC (before it was edited out of the question!):
⚠ You will not be able to play any DLCs with your copy of the game!
Any downloads are for the region where you bought the game. If you have pre-ordered, you should ask for a refund as soon as possible. I had the exact same problem with bloodborne.