UK Stocks-Factors to watch on March 19

March 19 (Reuters) - Britain's FTSE 100 index is seen opening down 16 points on Monday, according to financial bookmakers. * RIO TINTO: Rio Tinto has asked Swiss investment bank UBS to explore a possible public listing of its Pacific Aluminium smelting business on the Australian Stock Exchange (ASX), two industry sources said on Friday. * GLENCORE: Angolan state oil company Sonangol awarded its rare refined products buy tender to Glencore and Total, Sonangol sai