Audience measurement firm Taylor Nelson Sofres has confirmed its merger with German rival GfK in a probable attempt to stave off a third acquisition bid from Sir Martin Sorrell’s WPP. The pair agreed a nil-premium 50-50 merger that would create the world’s second largest market research outfit after Nielsen and would be valued at just under £2 billion. But most expect Sorrell to come back with another offer, following its 241.5p bid . TNS CEO David Lowden (via Times Online) said WPP would