Welsh vocalist Duffy(A&M/Universal) debut her album, "Rockferry," yesterday (March 9) at No. 1, while the single "Mercy" remained for a fourth week at the top. According to U.K. charts, "Rockferry" is Britain's fastest-selling album of the year as of yet. Duffy's arrival pushed Amy Winehouse's "Back to Black -- The Deluxe Edition" (Universal Island) down to No. 2. Also leaping into the top 10 were Danish pop band Alphabeat's "Fascination" (Charisma/EMI), which cruised 23-7; Westlife's "Us Against the World" (S/Sony BMG), which motored 40-8; and "Low" (Atlantic/Warner Bros.) by Flo Rida featuring Luciana, which inched up 12-9. On Billboard's European charts, Winehouse scored a second consecutive and ninth aggregate week at the helm of European Top 100 Albums with "Back to Black."