Linda, Google, Yahoo! etc. have UK and other country variants for example http://www.google.co.uk
is the UK specific version featuring primarily Great Britan focused sites & features. Research the different endings for different countries. Just like how Ebay and other sites look at the IP address of the computer & server your location tells them to gather content that is tailored to your current local. I've used Google AdWorks and you can select a radius from a specific address, a state, county, country etc. You could pick to have your ad campaign display your ads to people searching for real estate from Europe & Africa. Another good sourch might be to check out major news services in the areas that have online ad kits. Hope that's helpful.