By David Milliken and William Schomberg LONDON (Reuters) – Britain’s economy unexpectedly shrank 0.1% in March after a slump in car sales due to supply-chain problems, marking a weak end to the first quarter of a year when the risk of recession is looming. Gross domestic product grew by 0.8% in the first three months of 2022, the Office for National Statistic said – below the 0.9% forecast by the Bank of England and the 1.0% expected on average by economists polled by Reuters. Despite falling short of expectations, the growth between January and March is likely to mark a high point for the yea…