Preparing for Brexit, Britain may see new PM by early September

By Elizabeth Piper and Kylie MacLellan LONDON (Reuters) - Britain could have a new prime minister by early September, the ruling Conservative Party said on Monday, after David Cameron started laying the groundwork for his successor to trigger the country's exit from the European Union. The government is under pressure to fill a vacuum left when Cameron announced he would resign by October after Britain ignored his advice and voted to leave the 28-member bloc in last week's referendum. Triggering