If you paid by PayPal they will most likely refund you even if the seller doesn't want to. They are very helpful to buyers, whereas Ebay are more helpful to sellers (which is stupid in my opinion as Ebay owns PayPal anyway!)
But tell the seller you will file a complaint through both, if you get no response then do it and you should be fine. If they do not respond to the complaint through Ebay I don't think they can leave you feedback anyway.
I find the more polite you are the harder it is for someone to find a reason to leave you negative FB when you don't deserve it so just be the bigger person even if that seller does get nasty.
Good luck