(Reuters) - Britain's main index edged higher on Friday, led by financial stocks, but losses in stocks of global companies due to a rise in the pound and a slide in the shares of the world's largest spirit company Diageo capped the gains. The FTSE 100 climbed 0.1% by 0812 GMT, with banks overpowering steep falls in exporters including AstraZeneca and British American Tobacco . A rise in sterling meant the value of their U.S. earnings would drop. Shares of Diageo , sensitive to moves in..