Andy's just gone and impressed me even more by showing off his knowledge of Google (he comes up with more and more things every day!).
You're actually able to refine your sites to domains ending in a particular region such as .co.za or .co.uk or you can even tell if what the domain should include (all domains need to have "microsoft" in it).
The magic operators are:
And you can really work some magic with these as he's just shown. http://googletutor.com/ has everything you really need to know about Google there.