(Reuters) - London's blue-chip index fell on Thursday after two successive days of gains, dragged down by exporters which were hurt by a stronger pound as investors positioned for a higher-spending budget next month under a new British finance minister.The FTSE 100 ended the session 1.1% lower, derailed by steep falls in heavyweights Barclays and Centrica , while a rise in new coronavirus cases in China jolted broader risk sentiment. British utility Centrica skidded 15.3% after its 2019..