By Natasha Wynarczyk Shoppers rushing to buy last-minute Christmas gifts are predicted to splash out £3.31billion this weekend. With 38 million people set to shop on the high street and online, spending this weekend looks set to be 15% up on this time last year. “Super Saturday” today will drive £1.76bn in sales, making it the most lucrative day in the run-up to Christmas and giving retailers a welcome boost. Around 12 million people will hit the high street spending £1.15bn, while 6.8 million consumers will shop online, spending £0.61bn. On “Stampede Sunday” tomorrow, shoppers are expected to…