PROPERCORN’S HQ buzzes with youthful energy. Stroll through the front door, past the doorbell emblazoned with the words ‘Done Properly’, and you find yourself in one of London’s more life-affirming offices. The ‘guilt-free’ popcorn brand’s co-founders Cassandra Stavrou, an ex-ad agency employee, and Ryan Kohn, an entrepreneur since university, tell us how it all began…