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Do searches for UK sites but limit results to .co.uk
Then repeat for .com .org.uk .net etc.
If you need more than that then try also using a date operator to restrict results to a set period and then get rid of the duplicates.
If you need more than that you could try doing something similar with Yahoo and MSN and combining the results OR use common terms with positive and negative operators to split results e.g
widget site:co.uk -commomterm
widget site:co.uk commomterm
gives 2000 results, be careful to use terms that are likely to appear around an even amount of times otherwise you will skew your result set.
Other ways include:
restricting the file format to return Word or PDF etc
Pay Gigablast for a commercial feed and get 10,000 at a time from their data :)
Use common first or surnames as positive qualifiers - e.g. widget john site:co.uk
Use large town names as positive qualifiers (this will also allow you to filter out directory sites as they will have many appearances in the goegraphical lists.
IF you still need more then I think that buying Google would be the next step, certainly easier than combining all of that ;)
but no more than 10.. so it's poor .. even multi threading you use up 10 requests to get 100 results back .. when you only have 1000 request that soon adds up to .. api key query depletion