A helpful addition to the discussion - well done.

If it was me that was selling the laptop then so far I would have had my time wasted by a non-paying bidder, and I would have incurred costs associated with the Ebay advert and the amount of the winning bid, and when I re-advertise the item due to having been messed around there's a risk the item will not sell for as much as the original winning bid that was not honoured. I would therefore be perfectly entitled to seek recovery of my costs from the non-paying bidder who breached his legal obligation to complete the sale.