I think as a seller you shouldnt even consider offering non-insured post, its just common sense, its very nice if its cheap postage but if it arrives damaged the seller loses out all the time.
in this case i would just request to send it back for a refund, or he may just agree on a partial refund, i wouldnt open a case though, its always best to have a discussion about it. you will probably find you come to an agreement pretty quickly
