Specifically SCT013-000 (100A:50ma). Be careful to avoid the voltage types - SCT013-050, SCT013-030, SCT013-020, SCT013-005.
You can use the UK AC reference.
Negative. Those old phone supplies are chargers, not power supplies. I would recommend a USB power supply intended for a raspberry Pi. If you need a recommendation, I suggest a CUI. You should be able to get one with an Australian plug.