[drupal-support] Changing the default English Translation (locale)

Not actually working on multi-lingual sites (at this point), however... What I want is my 'en' 'translation' to be different from the default. I have on one site used the localization settings to add a new 'language' (which I called en-GB), however the sole purpose was to just change the default behavior. I didn't want to provide multiple 'translations'. It does work of course, just me being a fussy perfectionist. How are other people achieving the same thing? Cheers, Ross.