When it comes to SEO IP Addresses, specifically Geo-specific IP Addresses have no impact what-so-ever in regards to Google, MSN, and Yahoo! Unless you are doing PPC with the engines, then it might have some bearing on where you are advertising.
The "IP Specific", "IP Range" type of thinking is "90's" search engine philosophy. Which means... yes... back in the late 90's it did matter. But now in 2008 (modern day search engine optimization) it means just about nothing.
Now.. what will have some impact is the TLD. You could have a drastically different ranking with a .co.uk site on Google.com than you do on Google.co.uk etc...