A spate of pre-Christmas promotions drove an unexpected rise in retail sales last month, official figures revealed here Thursday.Retail volumes in October grew 0.6 percent compared with the previous month, the Office for National Statistics (ONS) said, defying expectations of a 0.2 percent fall.The better than expected performance came as retailers put on promotions to drum up trade before Christmas and as consumers bought winter clothes.Sales volumes had been expected to fall because it was thought the warmer weather would have put people off buying winter clothes, analysts said.The ONS said the food sector had seen a boost in October.Sales volumes in small stores rose 5.3% year-on-year - the biggest increase since November 2004.