(Reuters) - London's FTSE 100 inched higher on Monday as tobacco stocks jumped on Imperial Brands' buyback and dividend revision plans, but gains were capped by dampened hopes of a hefty rate cut by the U.S. central bank.UK blue-chip index rose 0.1% by 0800 GMT after opening lower in choppy trading, while the FTSE 250 mid-cap index also reversed early losses.Imperial Brands added 2.8% and sat at the top of the main UK index, after the tobacco company announced plans for a 200-million-pound..