OK I just found out about the command locale -a
which gives a list of installed locales. On my localhost, I had everything installed (and I noticed I was doing en_EN, but that still 'worked'), Anyway on the server, it was just fr_CH (not sure what C and POSIX is for) so my code for fr_FR wasn't working and I guess everything just defaulted to English somehow.
I found out that I had to manually edit the file: /etc/locale.gen
and uncomment the languages that I needed.
I then had to do sudo locale-gen
Run the command locale -a
to verify the list of locales
Then a simple sudo /etc/init.d/apache2 restart
and refresh the page - works :)