Is it worth having a .co.uk and a .com website for the same online business?

[Katy]

Hi!
I work for a small business which runs a cloud-based accounting tool. Since it's cloud-based, anyone can use / buy it - so we have users based in NZ, USA, Australia - as well as in our native Britain.
We use a .com domain, based in America - but we are considering a .co.uk domain, based here in Britain, too - not only to make our British users feel more at home, but also as a way to boost the company's profile and Google ranking.
However - from what I've heard, Google doesn't exactly love duplicate content - so the .co.uk website will have to be around 50% different, which is difficult since there is a limited amount we can say about the product!
Is it worth the effort of rewriting etc etc for the sake of Google ranking, or are we better off just concentrating on SEO for our .com website?
Thanks so much in advance - I hope this makes sense.