(Reuters) - London's main index bounced back on Monday after hitting a seven-week low in the previous session, when news of the first cases of the coronavirus in Britain hammered equities and fanned worries over its impact to the global economy.On the first trading day after Britain's exit from the European Union, the FTSE 100 and the FTSE 250 added 0.2% each.The blue-chip FTSE 100 was partly supported by exporter stocks such as Diageo Plc as the pound weakened, though gains were countered by..