That's wrong a contract does not have to be written down to come in to force.

Have a read of this Copyright in custom code: Who owns commissioned software?. As far as I can tell the OP would have a "moral right" and other rights to the work(s) he created, these rights have not been transferred to the client, so the client is infringing on the OP's copyright.

You may want to send a cease and desist letter to the client, reaffirming all your right in the work(s) and requesting that all infringing work(s) be removed from his website and computers with immediate effect. You don't necessarily need a solicitor to write this letter, but it might help to get in contact with one anyway (ring and get a ball park quote first ).