26-07-2016 11:24 PM
Congratulations on having the good sense to consider this possibility, which most buyer's don't!
EBay does warn buyers that their bids are binding. It's quite common for a buyer to be outbid, and then blithely buy the item somewhere else, only to find that someone has retracted a bid on the original auction and that they are suddenly the winning bidder!
As to how you can free up your bid, the short answer is that you can't unless you satisfy eBay's rather limited conditions for retracting your bid, see:
http://pages.ebay.co.uk/help/buy/bidding-overview.html