You should be able to return the bags within the UK if they were sent from a UK address.
You can ask Ebay to provide a return address if the seller won't.
However, the cost will be high, even to return with the UK, if you are sending large, heavy items as you have to use a tracked method.
You could go back to the seller and say you have changed your mind and would accept a 50% refund.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)