Have you checked the sellers "Feedback" rating on the site, this will often give a guide to how willing they may or may not be in dealing with complaints.
Not sure of the legal side of this, but I think that ebay do have a system for dealing with complaints, also if you paid with your Credit card, even though it may have been through "Paypal" it will be a good idea to let them know as well. This will depend on how much you have paid.
I do know that you can add a comment to the sellers rating, if you contact him again, mention this to him/her, saying that you will place an adverse comment if the issue is not dealt with. J.