Britain's FTSE 100 index is seen to open 41 points higher at 7,693 on Friday, according to financial bookmakers. * BHP: The union for Chile's Escondida copper mine said Thursday a contract offer presented by the company was unacceptable and threatened to strike unless changes were made. * BP PLC: Production at BP Plc's 413,500 barrel-per-day capacity Whiting, Indiana refinery was normal on Thursday after a report of flaring at the plant, said sources familia