If the US English version has been installed by mistake the WordPress language can be changed to UK English afterwards.

Go to WordPress translate: https://make.wordpress.org/polyglots/teams/

Find your language e.g. English (UK)

Download a copy of that translation’s WordPress and unzip

Copy the languages folder onto your server

To do this via bash zip up the languages folder and do the following:

$ scp /Users/Username/Desktop/WordPress/wp-content/languages.zip username@www.example.com:/home/public_html/wp-content/

$ ssh www.example.com

$ cd /home/public_html/wp-content/
$ unzip languages.zip
$ rm languages.zip

Login to the admin area of WordPress

Go to Settings > General

Set Site Language to English (UK) (it should appear now you have the languages file)