UK Stocks-Factors to watch on May 11

May 11 (Reuters) - Britain's FTSE 100 index is seen opening 11 points lower on Thursday, according to financial bookmakers. * BHP: Workers at BHP Billiton's, Cerro Colorado copper mine in Chile will strike for 24 hours in the coming weeks to protest recent layoffs and the company's general attitude toward miners, the main union told Reuters on Wednesday. * MYLAN/GLAXO: Generic drug maker Mylan NV on Wednesday said it disagrees with the reasoning behind the U.S. Food and Drug Ad