UK Stocks-Factors to watch on May 21

May 21 (Reuters) - Britain's FTSE 100 index is seen opening up 52 points on Monday, according to financial bookmakers. * BRITAIN ECONOMY: British households became much cheerier about their financial situation this month, according to a survey on Monday that will hearten Bank of England officials who think the economy's weak start to the year was temporary. * DRAX: British power company Drax will start work this month on a pilot bioenergy carbon capture and storage (CCS) project