UK Stocks-Factors to watch on Oct 27

Oct 27 (Reuters) - Britain's FTSE 100 index is seen opening down 0.5 percent on Thursday, according to financial bookmakers. * The UK blue chip index closed down 0.85 percent at 6,958.09 points on Wednesday, hit by weakness in banks and mining stocks after Lloyds Banking Group Plc and Antofagasta Plc fell after disappointing earnings updates. * BHP BILLITON: BHP Billiton said on Thursday its chief commercial officer, Dean Dalla Valle, who has led the company's response to the Sama