By Jennifer Sieg The John Lewis Partnership (JLP) is gearing up for a hiring offensive in the coming months as the retail group looks to bring in thousands of temporary staff for the festive season. Some 12,500 new workers are set to join its John Lewis department store and Waitrose grocery arm, up 4,100 on the same period last year. The retail group said the expansion of temporary roles is to prepare for what it anticipates to be its busiest period of the year in the run-up to Black Friday, Christmas and the New Year. “Whether making sure you’re choosing the right headphones or wanting inspir…