(Reuters) - UK midcaps broke a three-day losing streak on Thursday but still lagged the FTSE 100, with investors clearing the decks as Britons voted in a general election that could decide the fate of Brexit.The FTSE 100 added 0.6% with all sectors up by 0900 GMT. Broader sentiment was supported by the U.S. Federal Reserve signalling that interest rates would likely remain accommodative.The more domestically-inclined FTSE 250 only managed a 0.1% gain, with traders opting for a wait-and-watch..