Spelling correction ONLY works for US not UK spelling style

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I have, I believe, downlodad both the US an UK spelling packs, but never, in any version, have I EVER been able to spell check in UK spelling style. My default setting is US spelling - is that the problem? I do editing and people send me papers to edit in British style, sometimes. It would be a horrible task to change my default setting every time just to edit such a paper....help please.