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CloseReview for British English Dictionary by Ged Ridgway
Rated 5 out of 5 stars
@magicaxeman: you need to switch to using this dictionary after you install the add-on. Right-click an underlined word (like recognise in your case) and then under "Languages", select "English / United Kingdom".
By the way, this issue is actually arguably more complicated than MS Word etc. makes people think. While American English nearly always uses Z, British English stipulates "analyse" and not "analyze" but actually recommends "recognize" (with "recognise" as an accepted alternative, but not the first entry in the OED, which must surely be the authority on British English).
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