However, Tesco TSCO.L, Britain's biggest supermarket group, said last week that its prices were still falling. By James Davey LONDON, Oct 12 (Reuters) - British grocery prices increased 1.7% in the four weeks to Oct. 3 year-on-year, market researcher Kantar said on Tuesday, adding to pressure on households already facing soaring energy bills. With inflationary pressures mounting in the British economy, one Bank of England policymaker on Saturday told households to get ready for early interest rate rises.