Locking updates to a specific mirror

My ISP offers a freezone Ubuntu mirror (http://ftp.iinet.net.au/pub/ubuntu/) however Ubuntu is constantly pulling updates from a US server that is

• slower
• not inside my freezone

How can I force Ubuntu to use my local, freezone mirror before using others?

From ubuntu Farseeker

• Go to the menu System > Administration > Software Sources. There is a drop-down box labled "Download from:" where you can choose a mirror near you.

  If this doesn't work as planned (might not since you have a "custom mirror") then you can edit the file /etc/apt/sources.list by typing sudo gedit /etc/apt/sources.list in a terminal and pressing enter, if you need help you can type man sources.list in the terminal.

  A source of the unwanted traffic might be from security.ubuntu.com this is where the security updates comes from, they can be turned off, but it's not recommended!

  Farseeker : Thanks. My local freezone mirror is actually officially listed by Ubuntu as an official mirror. Bonus!
  From Source Lab