(For a Reuters live blog on U.S., UK and European stock markets, click LIVE/ or type LIVE/ in a news window) * FTSE 100 flat, FTSE 250 flat Jan 12 (Reuters) - British shares traded flat on Tuesday as a set of positive earnings updates helped boost confidence in the economy’s recovery, while investor worries over climbing coronavirus cases weighed on sentiment. The blue-chip FTSE 100 index was flat with energy and retail stocks gaining the most, with retailer Kingfisher being the top gainer on the index. The home improvement retailer rose 3.4% after reporting strong trade across its markets with fourth-quarter to Jan. 9 underlying sales up 16.9%. E-commerce retailer The Hut Group gained 3.1% after it raised 2021 revenue forecast by 10%, underpinned by its acquisition of Dermstore.com and a surge in online demand for its beauty products. However, gains were capped on Finance Minister Rishi Sunak’s warning on Monday that Britain’s economy would get worse before it got better, with the country now in its third national lockdown and as it struggles to contain the spread of COVID-19. (Reporting by Shashank Nayar in Bengaluru; Editing by Shailesh Kuber)