How to change your default locale on Ubuntu Linux

To check which locale you currently have as your default just run: locale

Changing the default locale is a little different on Ubuntu compared to most Linux distros, these are the steps we needed to go through to get it changed:

Add the locale to the list of 'supported locales'
Edit /var/lib/locales/supported.d/local and add the following line:
en_GB ISO-8859-1

Regenerate the supported locales
Run sudo dpkg-reconfigure locales

Change the default locale
Edit /etc/environment and ensure the LANG and LANGUAGE lines read as follows:
LANG="en_GB"
LANGUAGE="en_GB:en"

Reboot!

Rerun locale to check that your default locale is now en_GB