THE saga of the failed bid for the British Co-op took a new twist yesterday with the revelation that the Serious Fraud Office is to launch an investigation. The probe will centre on a deal in January 1995 between the Co-operative Wholesale Society (CWS) and Hobson Group, a company then controlled by Mr Andrew Regan. He is the City whizzkid who last week failed in his ambition to launch a bid for the Co-op. The investigation is thought likely to focus on a £2.4 million sterling payment made by the CWS to a Cayman Islands' based company called Trellis International.