By Carolyn Cohn, Tommy Wilkes and Carolina Mandl LONDON/NEW YORK (Reuters) – Calls to the Bank of England saying some British pension funds were struggling to meet margin calls began on Monday. By Wednesday they were getting more urgent and coordinated. Wild gyrations in financial markets in response to a government “mini-budget” on Sept. 23 meant that swathes of Britain’s pension system were at risk, raising widespread concerns about the country’s financial stability. British Finance Minister Kwasi Kwarteng’s statement had included dramatic plans to slash taxes and pay for it with borrowing w…