LONDON—British grocery prices increased 1.7 percent 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. A survey published on Monday by pollsters YouGov and consultancy CEBR meanwhile said consumer confidence has fallen to a five-month low. Kantar said prices are rising fastest in markets such as savory snacks, cat food, and crisps while falling in fresh bacon and vegetables. “In real world terms, the average household had to spend an extra £5.94 [$8.08] on groceries last month than they did at the same time last year,” said Fraser McKevitt, head of retail and consumer insight at Kantar. “The typical household spends £4,726 [$6,421] per year in the supermarkets, so any …