UK Stocks-Factors to watch on May 10

May 10 (Reuters) - Britain's FTSE 100 index is seen adding 0.2 percent on Thursday, according to financial bookmakers. * Rolls-Royce Holdings Plc's Chief Operating Officer Simon Kirby will leave the company in June as the British manufacturer looks to streamline its business. * Royal Bank of Scotland Group Plc said on Wednesday it had agreed to pay $4.9 billion to resolve a U.S. Department of Justice probe into its structuring and sale of mortgage-backed securities ahead of the