UK Stocks-Factors to watch on May 17

May 17 (Reuters) - Britain's FTSE 100 index is seen opening down 4 points at 7,730 on Thursday, according to financial bookmakers. * ROYAL MAIL: New chief executive of Royal Mail, Rico Back, has been paid nearly 6 million pounds ($8.13 million) to buy him out of his contract in a move that could spark fury among former state-owned company's trade unions and shareholders. http://bit.ly/2ILWaJ6 * MOTHERCARE: Britain's Mothercare Plc will shutter 50 stores in the UK and bring back