Changing Auto-correct language

Hey Team.

I purchased my macbook in Canada over 3 years ago but have been living in France since. Recently my harddrive exploded and I had to get a new one, which meant they reloaded OSX and all that jazz. Now my auto-correct language is French. I've been trying everything I can think of to reset the language to English (Canadian, American, British, anything really) but have had no luck. As I write this everything is underlined in red as very few of these words can be found in a French dictionary.

I've tried changing the language/dictionary in Firefox and Word but alas it still autocorrects (or at least identifies mispelled words) in French. This is becoming quite a hastle.

Any tips or advice are great appreciated.

Thanks.