UK Stocks-Factors to watch on May 3

May 3 (Reuters) - Britain's FTSE 100 index is seen opening flat on Tuesday, according to financial bookmakers. For more on the factors affecting European stocks, please click on * The UK blue chip index ended down 1.3 percent at 6,241.89 points on Friday, hit by a fall in the shares of Royal Bank of Scotland and airline IAG. * HSBC: HSBC posted a 14 percent drop in its first-quarter profit, as the lender's investment banking unit saw trading income tumble in the grim global marke