Change default Google localisation in Firefox in Ubuntu
Be default in Firefox on Linux, when you use the Google search up in the address bar it defaults to a search of google.com instead of my preferred google.co.nz. If you want to change this, go look in /usr/lib/firefox[--version--]/searchplugins/google.xml and swap out the .com for .co.nz (or whatever localised Google site you prefer).

This workaround doesn’t seem to work with with FF 5
hmmm… actually it works. You just need to modify file for your current locale.
/usr/lib/firefox-5.0/searchplugins$ ls
common en-AU en-GB en-US en-ZA