UK Stocks-Factors to watch on May 22

Britain's FTSE 100 index is seen opening 21 points higher at 7,350 on Wednesday, according to financial bookmakers. * BHP: Global miner BHP Group on Wednesday said it plans to expand its nickel sulphide operations amid an expected boom in demand for the material in electric vehicle batteries. * ACACIA: Canadian miner Barrick Gold Corp said on Tuesday it has proposed to acquire all of the shares it does not already own in Acacia Mining Plc through a share-for-s