LONDON (Reuters) – British consumers are reacting to the cost of living crisis by trading down in both stores and products, switching from supermarkets to discounters and from branded to lower priced and private label products, a report from consultants McKinsey said on Monday. Surging prices are causing the biggest squeeze on UK household incomes since at least the 1950s and consumer confidence is at near record lows. Britain’s consumer price inflation rate hit 7.0% in March and economists polled by Reuters expect it will leap to 9.1%, its highest since 1982, when April’s data is published on…