Have you explained all of this to the insurance company? If not, do so (calmly) and explain that it wasn't intentional. Also ask them how they rated the premium - if it was based on you (as a younger driver) you may have actually paid the correct premium for the risk. They are still within their rights to refuse to pay, as they provided insurance based on incorrect facts, but they may look at their decision again. If they still refuse, find out what their complaints procedure is, follow it, and if still no joy, contact the Ombudsman.