APNIC finding IP ranges for an ISP
Heres a quick and dirty solution;
Go here http://wq.apnic.net/apnic-bin/whois.pl
Look up one of the IPs you know of in the range
Look for: mnt-lower
Change the Inverse attributes to mnt-lower
Then do a look up for: MAINT-AU-TIAR-AP (example)
Now click search and all the ranges will come up.