(Corrects revised July month-on-month data to -0.6% from 0.6% after error in Nationwide table) LONDON, Sept 1 (Reuters) - British house prices rose by 2.1% month on month in August after a -0.6% fall in July, despite the phasing-out of a tax break for purchases in England and Northern Ireland, figures from mortgage lender Nationwide showed on Wednesday. House prices in August were 11.0% higher than a year ago, a bigger increase than the 10.5% rise Nationwide recorded in July and bucking economists’ expectations in a Reuters poll for a slowdown to 8.6%. (Reporting by David Milliken. Editing by Andrew MacAskill) Our Standards: The Thomson Reuters Trust Principles.