British English in OS X


Just wondering, how do I get OS X to actually use British English? I'm in the US, so I didn't go buy it somewhere in the UK. I just prefer BE and it doesn't do that in the Finder or in any of my apps (particularly IE) and in the spell-checker. I did the thing witht he international panel already, but I mainly just would like to have it in the spell-checker. If anyone knows how to get this, please tell.