(Reuters) - The UK's FTSE 100 retreated on Wednesday as data showed inflation fell to its lowest since August 2016 in the latest economic blow from the coronavirus outbreak, with investors also digesting another mixed bag of quarterly earnings reports.The blue-chip FTSE 100 was down 0.2%, with the banking index tumbling 1.2% on increased bets of negative interest rates.The mid-cap FTSE 250 lost 0.3%, snapping a three-day winning streak as a report also questioned positive data from an..