LONDON — Alberto Iglesias swept the board at the World Soundtrack Awards Saturday, clinching composer and soundtrack for the music he wrote for “The Constant Gardener.”The awards were presented at a special ceremony during the Flanders Intl. Film Festival in Ghent. Gustavo Santaolalla won the Public Choice Award for his Oscar-winning “Brokeback Mountain” soundtrack and Evanthia Reboutsika was named Discovery of 2006 for the music of “My Father & My Son.” The song “Our Town” from pic “Cars” by Randy Newman and James Taylor was named original song written for film. A Lifetime Achievement Award went to veteran German composer Peer Raben. He was absent for health reasons, so the actress-singer Ingrid Caven collected it on his behalf.