i had the same with a sump baffle i won for peanuts and the bloke tried to charge me £45 for postage to try and boost the price up a bit, even though he'd listed the item with no reserve and a £12 postage fee.

in the end we came to a compromise and i agreed to pay him £20 postage.

at the end of the day a bargain is a bargain and your bid and his listing is a binding contract.

report him if he wont talk to you mate