Christina Aguilera's single "Dirrty" featuring Redman (RCA) sprang a major chart surprise in the U.K. yesterday (Nov. 24) by holding at No. 1 in the face of "Pop Idol" victor Will Young's new release, which had the extra bonus of a charity tie-in. "Dirrty," which entered the chart at No. 1 last week, was widely expected to cede the top spot to Young's "Don't Let Me Down"/"You and I" (S/RCA).