LONDON, Sept 15 (Reuters) - British inflation surged last month to its highest level since March 2012, official data showed on Wednesday. Consumer prices rose by 3.2% in annual terms after a 2.0% rise in July, marking the sharpest increase in the annual rate since detailed records started in 1997. A Reuters poll of economists had pointed to a reading of 2.9% for August. (Reporting by Andy Bruce; Editing by Kate Holton)