British retailer Marks & Spencer on Tuesday said sales at its stores rose by 0.5 percent in the final three months of last year, helped by a better-than-expected performance at its food unit. The group\'s overall sales in Britain grew 0.5 percent in the 13 weeks to December 31 compared with a year earlier, M&S said in a trading update published as much of Britain\'s retail sector struggles to overcome a weak economic climate. Food sales rose 3.0 percent, above analyst expectations for a gain of 1.5 percent, according to Dow Jones Newswires. Sales of general merchandise, including clothing, dropped 1.8 percent in the period. \"In light of the ongoing macro-economic uncertainty, we expect trading conditions to remain challenging,\" M&S said.