here are three links for iTunes:
main versionsremixesHouse Agents Dubhere are some other places you can buy it:
Tesco DownloadWoolworths DownloadXpress BeatsTunetribeNapsterDJ DownloadTrackitdownEasymusic7digitalJunoWippitAudiojelly then search for Do It Yourself
Beatport then search for Uniting Nations
Oxfam (needs Internet Explorer on Windows)
HMV Digital (needs Internet Explorer on Windows)
Tiscali (needs Internet Explorer on Windows)
3MusicStore (3 mobile customers only)
If you buy each remix separately, each one counts as one sale on the chart (whereas if you buy all the remixes in a bundle, that only counts as one sale in total).