* Activist Bramson's Sherborne vehicle owns 4.2 pct of 3i * 3i says it has "wasted no time" to restructure * 3i shares have risen 65 pct since mid-2012 LONDON, March 1 (Reuters) - Private equity group 3i defended its turnaround strategy on Friday after it emerged that activist investor Edward Bramson had increased his stake in the company.