They are handled in different places. But you could keep your system in your
preferred language and only ask for "en_UK" (or, maybe, the system locale)
when executing a command whose output will be shown to international users
(for help). Like stas730 wrote, you can redefine LC_ALL to do so. For
example, my system speaks French:
$ ls --version
ls (GNU coreutils) 8.21
Copyright © 2013 Free Software Foundation, Inc.
License GPLv3+ : GNU GPL version 3 ou ultérieure
C'est logiciel libre, vous êtes libre de le modifier et de le redistribuer.
Ce logiciel n'est accompagné d'ABSOLUMENT AUCUNE GARANTIE, dans les limites
autorisées par la loi applicable.
Écrit par Richard M. Stallman et David MacKenzie.
But I can precede the command with "LC_ALL=C" to use the default locale:
$ LC_ALL=C ls --version
ls (GNU coreutils) 8.21
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later .
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Written by Richard M. Stallman and David MacKenzie.
