Hi all. This is my first guide on ebay about mistakenly pressing "payment sent button" when you are trying to pay via paypal. I had the same problem too, but I have found the answer after reading a few FAQ's.
First of all you log into your paypal account and click on send money tab. After you got 2 sub headings one is pay for anyone, the other is pay for ebay items. Click on pay for ebay items and simply enter your ebay ID and Password and submit. It will give you your list of unpaid payments of your winning auctions that you accidently hit "payment sent" and you can pay for it here. Hope this helps all those who went into same trouble as I did =)