UK Stocks-Factors to watch on April 21

April 21 (Reuters) - Britain's FTSE 100 index is seen opening up 15 points, or 0.2 percent higher on Thursday, according to financial bookmakers. For more on the factors affecting European stocks, please click on * The UK blue chip index closed up 4.91 points, or 0.1 percent on Wednesday at 6,410.26, at a fresh year high after a rally in the price of oil spurred gains in commodity-related stocks. * SKY: Mediaset and Sky Italia, a unit of Sky Plc, have been fined 55.4 million euros