You should not have to pay a deposit for anything you buy on Ebay.
If the seller is asking for a deposit, and has a really long date for you to get your item, it is likely they are out to obtain your money without providing you with anything.
Once the latest estimated delivery date has passed, you have 30 days to make a claim through Ebay, and you have 60 days from the sale date to leave feedback.
if you are still in time, you may be able to get help from your payment provider.
"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)