If it is a UK business seller and their contact details (phone and email) are not on their listings, try google.
Business sellers quite often have a presence outside of Ebay.
Ebay won't get involved outside of the 30 days the Ebay Money Back Guarantee allows.
You may be in time to start a payment dispute/chargeback. See what your payment provider says.
"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)
