I had a look just now and the only thing they "translated" was the "Welcome to the official Civilisation III Website" message at the top. Otherwise, absolutely identical to the US version in terms of spelling, blurb, news, etc. The word "pathetic" springs to mind
PS it should also be noted that, according to any good UK English dictionary (esp. the Concise Oxford), the spelling "civilization" is perfectly British and is, infact, preferred in academic circles over "civilisation".