This module will help you in getting auto store-switch for your customer coming from a particular country.
Use Helper (Data.php) to map stores to the countries. A example is given below which i have used in module.
protected $_countryToStore = array( 'FR' => 'French', 'BE' => 'French', 'CH' => 'French', 'DE' => 'German', 'AT' => 'German', 'UK' => 'English', 'US' => 'English', 'UA' => 'English', 'CN' => 'English', 'JP' => 'English' 'IN' => 'English' );
Use this URL to find the standard country code http://dev.maxmind.com/geoip/legacy/codes/iso3166/
This module requires a maxmind IP service which can be used by installing this module https://github.com/magento-hackathon/Sandfox_GeoIP
This MaxMind module returns the Standard Country Code, on the basis of which we switch stores in magento store.