White Horses was written by Michael Carr and Ben Nisbett for the UK import of Yugoslavian/German TV show Ferien in Lipizza, it was credited to "Jacky", who is actually Jackie Lee. The theme song was so successful that it was apparently dubbed back onto non-English versions of the show.
Dean & Britta covered the song on their second album, Back Numbers, in 2007.
The single has sold out but you can get the Sonic Boom remix on Cathedral Classics Vol 1 for a couple of quid - which is quite the bargain!
Here's a live version recorded for the World Cafe in 2007
MP3: Dean & Britta - White Horses (live on WXPN, 8 March 2007)
The song has been covered by a hatful of cool folk, most of whom you can find in this post on Everything's Swirling.