I'm not so sure. In "real" auctions, the auctioneer uses his discretion regarding reserves; if the highest bid is nearly there he may well accept it. Similarly, if the final bid is, in his opinion, too low he may well pass the item as unsold.
How about if the highest bid was, say, £28 and your reserve was £30. Would you like the option to accept that bid after all, or do you want to re-list with a lower reserve and the chance that your potential buyer had gone elsewhere?