If you want to use WordPress in the Queen’s English, you’re in luck. There’s an en-gb translation and it’s been updated for WordPress 3.8. With the new admin design, British English WordPress installs will spell words like “colour” and “customise” in the proper English style.
The easiest way to get an installation that uses proper English is to download the full package from the en_GB WordPress homepage. This download offers the latest version of WordPress with the British translation files already in place and referenced in wp-config.php. Please note that installing this entire zip package is only useful if you’re starting from scratch.
How to Manually Add Translation Files for an Existing Site
If you have an existing site where you’d like to add British translation files, here’s how:
Step 1. Download the British English .mo language file from the en_GB homepage. You can pull this out of the /languages/ folder in the package. As a bonus, if you’re using Twenty Fourteen, you can also find a theme translation within this folder.
Step 2. Create a new directory under wp-content called languages: /wp-content/languages/
Step 3. Upload the en_GB.mo file to the languages directory.
Step 4. Add this line to your wp-config.php file in the languages section:
Save your changes to wp-config.php and upload it to your server. You should now have proper English displayed throughout your installation.
Note that this same process applies to any other language files as well. Hopefully, this small courtesy will bring some cheer to our friends across the pond!