Top Conservatives weigh leadership ambitions in EU vote

By Kylie MacLellan LONDON (Reuters) - As senior British Conservatives prepare to take sides in a referendum on European Union membership, some will be more focussed on their own future - and their chances of succeeding Prime Minister David Cameron - than that of the country. While Cameron will allow his ministers to choose whether they support the 'in' or 'out' campaigns for the upcoming national vote, those hoping to become the next Conservative leader face a dilemma. If they come out in favour