"orientated" may be a perfectly cromulent word -- and may generally be a synonym for "oriented" -- but the phrase describing the programming paradigm is "object oriented" not "object orientated". Just as "functioning" is indisputably a good word and may be a rough synonym for "functional", but if you talk about about Haskell as a "functioning programming language", you may be correct in a sense, but it won't be as a statement about the programming paradigm it supports.
I don't dislike the word "orientated" (it is a real word), nor would I discourage it's use on either side of whatever pond. It's simply not correct to use it in the particular and very specific "object oriented" context. Much like the often mis-camel-cased "SmallTalk", it is incorrect.
Had Alan Kay coined the term "object orientated", I would use it without question.