To dogfood this, rent a VPS in Australia and put a test environment there. Should be about 200ms ping or a bit higher. How it runs for you is how Australian users are seeing your site, even if their last mile connection is fiber.
Example pings from here in Australia (FTTP)
PING news.ycombinator.com (209.216.230.207): 56 data bytes ... --- news.ycombinator.com ping statistics --- 40 packets transmitted, 40 packets received, 0% packet loss round-trip min/avg/max = 154.980/155.832/156.990 ms
round-trip min/avg/max = 164.218/164.860/165.764 ms
rtt min/avg/max/mdev = 201.881/245.543/350.600/48.713 ms
Example pings from here in Australia (FTTP)
FTTP except via WiFi: Or through the mobile network: