Britain is heading for strong growth in 2011 and 2012 on the back of exports and investment, but there will be only a modest upturn this year, according to Ernst & Young Item Club, to be published tomorrow. It predicts weak growth of 1% this year, giving way to 2.7% next year and 3.4% in 2012 - close to Treasury forecasts that have been widely dismissed as unrealistically optimistic. The prediction comes ahead of a key week of economic data, which will culminate on Friday with the release of figures for first-quarter gross domestic product. The Sunday Times