UK Stocks-Factors to watch on Sept. 1

Sept 1 (Reuters) - Britain's FTSE 100 index is seen opening up 16 points, or 0.2 percent, on Thursday, according to financial bookmakers. * The UK blue chip index closed down 39.28 points, or 0.6 percent, on Wednesday at 6,781.51, hit by a late slump in the energy sector, although the index posted its third monthly gain in a row. * ROLLS-ROYCE: ANA Holdings Inc, Japan's largest airline, said on Wednesday it will replace all 100 Rolls-Royce engines on its fleet of Boeing 787 Dreamli