You'll need to get business van insurance (also called commercial van insurance) which permits the carriage of goods for hire or reward. This will be more expensive than social only or carriage of own goods insurance. The cost will depend on the size of your van, the type of deliveries you are doing (if you're doing multi-drop deliveries in a small area this will be seen as 'less risky' than high mileage, long-haul routes), where you keep you van overnight, and the amount of voluntary excess you choose to pay. According to GoCompare the average cost of a comprehensive courier policy was £1,080 in December 2020, rising to £1,244 for long distance deliveries. Also bear in mind that not every insurance provider will cover couriers.