LONDON—British fashion retailer Next raised its full-year profit outlook for a fifth time in 10 months after beating guidance for sales in the run-up to Christmas, boosted by an unexpected revival in demand for adult formal and occasionwear. As the first major UK retailer to update on Christmas trading, Next set a high bar on Thursday for rivals as it reported a 20 percent rise in full-price sales in the eight weeks to Dec. 25 versus the same period in 2019 before the pandemic began. Guidance had been for a rise of 10.2 percent. Next did, however, caution that pressures on consumers’ finances, such as higher food prices, energy costs, mortgage rates, and taxes, pointed to a tougher trading environment in 2022. It also flagged that its own prices would rise 3.7 percent in the first half of 2022 and 6 percent in the second half due to higher freight …