By David Milliken LONDON (Reuters) – Britain is becoming a more closed economy due to Brexit, with damaging long-term implications for productivity and wages which will leave the average worker 470 pounds ($577) a year poorer by the end of the decade, a study forecast on Wednesday. The report was written by London School of Economics associate professor Swati Dhingra – who will join the Bank of England’s Monetary Policy Committee in August – and researchers from the Resolution Foundation think tank. The COVID-19 pandemic, which struck just after Britain left the European Union in January 2020,…