Could someone please tell me how to have UK English, instead of US Craplish?

I am fed up with this. Every time I am writing an email or something in a blog or here, these meaningless spelling recommendations and red error given on correctly spelled words are beyond my toleration. Colour, red underline, and so many other words which I don't remember right now, disgusting. Is there any way to have UK English rather than US when I am typing on Firefox or Chrome? I once changed the system language in Windows 7 to UK English and if I remember right it changed the positions of the symbols in the keyboard, the '@' was moved to something else from Shift+2 combo, which is weird!
Any help?

Yes. Along with the language, keyboard orientation also gets change, like # will become Pound sign.

Take a look at British and American keyboards - Wikipedia, the free encyclopedia

You can change in settings for Chrome as well as FF. Have done myself. Both my browsers use UK English for spell check .