Hi Mary

Theoretically the buyer is obliged to buy, in practice if they don't want it you can't make them pay.

You have two options.  1) Cancel the transaction; you will get your final valuation fee backs, the buyer can still leave you feedback

2) Wait four days and open a non paying bidder dispute;  if they don't pay and it closes (after 7 days) you get your final valuation fee and the buyer can't leave feedback.  If it prompts them into paying they can still leave feedback as normal (they may feel bitter)

Check the buyers feedback left for others - if they seem reasonable the mutual cancellation is probably the nicest option.