UK Stocks-Factors to watch on Dec 7

Dec 7 (Reuters) - Britain's FTSE 100 index is seen opening between 31 and 35 points higher, or up as much as 0.52 percent on Wednesday, according to financial bookmakers. * The UK blue chip index closed up 0.5 pct at close at 6,779.84, supported by a rally in bank stocks. * RIO TINTO: The copper market will go into deficit by 2020, just when Rio Tinto's extension to the Oyu Tolgoi mine in Mongolia comes onstream, the company said on Tuesday. * BHP: Brazilian iron ore miner S