By Jennifer Sieg Alexandra Birtles was just shy of 33 when she realised climbing the corporate ladder was no longer enough to keep her happy, even if it meant giving up a healthy salary. “Life’s too short,” Birtles recalled telling herself the moment she realised she had an itch she couldn’t scratch. Now co-founder and chief executive of In Good Company – an online platform used to find socially-minded businesses in London – Birtles said it all began when she realised fulfilment meant more to her than a corporate climb ever would. The business allows Londoners to seek out everything from ethic…