Sniping is allowed, it can either be through a Company who bids for the bidder in the last few seconds, or manually a bidder tries a final bid as near to end as possible.
If a sniping bid is placed, it could be a £1000, but would only get to that figure if someone else bid something like £990, so the possibility of overpaying is very unlikely, and I doubt the reason for winning bidders asking to cancel.
I would be inclined assuming winner does not pay, to cancel on day 5 for non payment.
Today I see that ebay has at last admitted that a seller does not have to cancel, and that any negative feedback left by buyer, would be removed on appeal.
