With different languages and domain names (I.e. German, Russian, Chinese, etc.) you should be OK.
It gets a lot trickier with the .ca and co.uk. I would not recommend duplicating the English website on those two domain extensions. I would recommend making unique websites for these two utilizing small language differences like "optimization" versus "optimisation".
I good example of all different languages is what large companies like Kelkoo does:
http://www.kelkoo.com/