LONDON, Sept 10 (Reuters) - Britain’s economy barely grew in July, rising by just 0.1% from June, the weakest expansion since January when the country went back into strict lockdown rules, official data showed on Friday. Economists polled by Reuters had mostly expected month-on-month growth of 0.6% in gross domestic product. Reporting by William Schomberg and Andy Bruce; Editing by Paul Sandle Our Standards: The Thomson Reuters Trust Principles.