two strongest location signals are 1) the ccTLD and 2) hosting location.
If you decide to change hosts, be sure that you’ve selected a Geographic Target in the Webmaster Tools console well ahead of time. If it’s appropriate, sign up for Google’s Local Business Center, and the corresponding services for Yahoo! and Bing as well. Post the complete address of the business on your most important pages. Since these are things Google looks at, you’ll want to have them all working in your favor.