(Reuters) - London's FTSE 100 headed higher on Tuesday as a batch of upbeat quarterly earnings updates outweighed concerns about a slower economic recovery as countries balance reopening businesses with avoiding a potential jump in COVID-19 cases.The blue-chip FTSE 100 gained 0.5%, with Vodafone , the world's second largest mobile operator, jumping 3.4% to the top of the index after meeting full-year profit expectations and saying it was seeing significant increases in data volumes.Home..