It appears that you need to exercise more diligence when shopping online to avoid making those mistakes that cause you to wish to cancel transactions. The time to decide if you want to purchase an item is prior to placing your order or bid.
I'm not quite sure where you get the idea that it is reasonable for buyers to be allowed to cancel transactions. As it is, buyers are permitted to request a cancellation but sellers are not required to comply with the request. Here is why your idea is not reasonable:
1) Once you hit the buy now button, the item is removed from available sale. Thus the seller is taking a loss of time that the item is not available to be sold because of the cancellation.
2) The seller has already been charged the FVF (eBay's Commission) the moment that the buyer places the order.
3) If the item has been paid for through PayPal at the time of purchase, the seller has already lost the PayPal fees from that transaction.
4) The seller loses time in having to relist the item and as the saying goes, "Time is money."
For the above items it is the not reasonable to give buyers the unilateral ability to cancel transactions. Thus, while the buyer may ask to cancel, it is the seller that must remain in control of the final decision.
While I'm not very familiar with the laws governing auctions in the UK, here in the US placing a bid on an item being sold at auction is, under the laws of most states governing auctions, deemed to be a legally binding contract if the bid is the winning one. Thus a bidder that then wants to cancel the sale after its closing could find themselves in litigation if they could simply cancel the transaction on their own.
Thus there is nothing to fix.
"It is an intelligent man that is aware of his own ignorance."
