Bidder wants to cancel transaction In the last hour of bidding.What do I do as a seller to accept this cancellation
Until the end of the auction there hasn't been a transaction to cancel.
If they end up being the winning bidder and don't pay, after 4 days of non-payment open an Unpaid Item Dispute and close it after a further 4 days of non-payment.
They will get a strike on their account and you will get your selling fees back from eBay and will be able to relist your item if you wish.
The non-payer will not be allowed to leave you any feedback once the dispute has been closed.
Add them to your blocked bidders list.
Blocked bidders list:
here you go