Houses sold at auction frequently sell for their guide price. In fact, and this is good news for sellers in particular, auction properties will often sell above their guide price.
Of course this cannot be guaranteed, and is dependent on a number of factors including the number of bidders, the housing market at the time of sale, the auctioneer's efforts, and how well a house has been marketed.
Buyers will need to bear this in mind when bidding on a property, taking into account their set budget and how much they can afford to pay for a property and the fees involved.