Firstly i'm guessing the OP has genuine interest in the house. The EA usualy states these "offers" because thats a price the vendor will not go below, by saying you would considder an amount close to it, you are giving the EA room to go back to the vendor, with the chance of a slightly lower offer. But as i said you have not named any amount but atleast you know the 298k is bull and they will take below it. The balls in your court then.
I aggree with Parkmagic here. Say you have a genuine interest in the house, but at the right price, you dont have to say what the price i.e. "a fair bit" below the asking price.