To transfer your insurance from one car to another you will need to contact your insurer in the first instance to advise them as to your new vehicle details. Your insurer will then recalculate your price and offer you the option to either insurer your new vehicle or cancel your policy. You will have to pay either a mid-term-adjustment or cancellation fee to cover the administration involved in changing your insured car.
Please be advised that, if you choose to cancel your policy it is up to you to get alternative cover. Please be aware that it is against the law to drive a vehicle on a public road without insurance.