* FTSE 100 up 0.5 percent * Yellen says Fed needs to do more to aid economy * Sainsbury leads consumer staples higher * Centrica falls after warning on earnings By Alistair Smout LONDON, Nov 14 (Reuters) - Britain's top shares rebounded on Thursday, led higher by energy stocks after the Federal Reserve's Janet Yellen eased worries the U.S. central bank may start scaling back its stimulus programme this year. Yellen, in remarks released ahead of the Senate hearing on Thursday to confirm her as new Fed president, said the central bank had "more work to do" to help the economy, indicating she was in no hurry to start trimming the bond-buying programme that has fuelled an equity rally this year. "Yellen is a well-known dove, so won't tighten very soon. I expect it to be around the end of the first quarter of 2014," Robert Quinn, chief European equity strategist at S&P Capital IQ, said. With appetite for risk boosted by the Fed's comments, cyclical stocks such as energy companies rallied, adding a combined 20 points to the index's gains. The FTSE 100 rose 31.92 points, or 0.5 percent, at 6,661.92 by 1136 GMT, recovering from a sharp fall on Wednesday when the Bank of England gave a stronger forecast for the UK economy, bringing forward expectations for when interest rates will rise and so sending sterling higher, hitting exporters. Consumer staples contributed 6 points to the index and were led higher by food retailer Sainsbury, which climbed 2.7 percent towards the top of the FTSE 100 leaderboard as brokers raised recommendations and target prices across the board following results on Wednesday. British luxury brand Burberry was up 1.4 percent after first-half sales exceeded 1 billion pounds ($1.6 billion) for the first time. "The results are another welcome indication of the healthy position (CEO) Angela Ahrendts leaves the firm in when she passes the reins onto Christopher Bailey next year," Toby Morris, senior sales trader at CMC Markets, said in a note. However, earnings remain a concern for investors in Europe. Equities have re-rated above long term averages, even though profits and revenues continue to disappoint. Fifty percent of firms in Europe have missed analysts' earnings forecasts in the third quarter so far, while 63 percent have missed sales estimates, heaping more pressure on margins. British Gas owner Centrica, one of Britain's big six utilities under fire from politicians for hiking bills, fell 4.2 percent, topping the list of FTSE fallers and dragging the utilities sector lower after it warned that earnings would not grow this year. Drinks can maker Rexam fell too, down 1.8 percent after it warned on the outlook for trading in Europe where it generates more than 23 percent of its revenues, according to Thomson Reuters data.