By Shreyashi Sanyal (Reuters) -Britain’s FTSE 100 closed lower on Friday as Wall Street slipped after strong jobs data raised fears about faster U.S. interest rate hikes, but a weakening pound helped the UK blue-chip index log its third consecutive week of gains. The FTSE 100 dipped 0.1%, with shares in WPP, the world’s largest advertising group, falling 8.8% after its annual sales outlook failed to excite investors expecting stronger forecasts. The midcaps index finished down 0.5% as the global mood soured after a solid U.S. jobs report for July bolstered the case for the Federal Reserve to p…