By Laura McGuire Next has raised its profit guidance for the fifth time in a row thanks to a bumper Christmas trading period. In a trading update this morning, the fashion favourite said it expects profit before tax for the year to increase by £20m to £905m. The retail giant said In the nine weeks to 30 December, full price sales were up 5.7 per cent versus last year. This was £38m better than its previous guidance for the period. Next, led by City grandee Lord Simon Wolfson, also credited a reduction in stock for its strong performance. The retailer headed into the end-of-season sale with 12 …