We had a house with a sitting tenant and put it up for sale by auction through an estate agent, paying £1,000 for this service. In the event we contacted a private buyer before the auction brochure went into print, agreed a price and sold the house. Now the estate agent wants a further £1,000 from us, even though they didn’t sell it. We only got £56,000 for the property.
Whether your agent is entitled to the money will depend on the agreement you signed up to. If you gave them sole selling rights you will probably be obliged to pay them commission (and by the look of it, expenses) even though you sold the house yourself. Given the amount of money involved you should probably ask a solicitor to check the agreement however.