This is a very odd tale. If the applicant was hostile from the onset, surely such a behavioural problem would already have been known to the RF/FTO instructors?
I would have no qualms about ringing the CAA and recommending that the applicant should be formally assessed by a psychologist before being permitted to fly again.
Anyone subjecting and instructor or examiner 'to a vile onslaught of personal verbal abuse' has no place at the controls of an aircraft.