Higher energy prices and a rise in long-term interest rates are likely to weigh on British economic growth next year, the International Monetary Fund warned on Tuesday, even as it revised up its forecast for expansion this year. The IMF predicts Britain's economy will grow 1.3% this year, up from predictions of 1.0% in July and 0.8% in April, before slowing to 1.2% growth in 2027, putting Britain in the middle of the pack among major advanced economies.