A 32-year-old woman presents with sudden onset shortness of breath and pleuritic chest pain, 2 weeks after a long-haul flight. Her heart rate is 115 bpm, respiratory rate 22/min, BP 120/80 mmHg, and oxygen saturation 94% on air. Her Wells score for PE is calculated as 5 (HR >100, recent travel >4hrs, clinical signs of DVT not present but PE most likely diagnosis). According to NICE NG158, what is the next appropriate step in management?