I have had this with colleagues of mine, I asked them if they...

I have had this with colleagues of mine, I asked them if they (the buyer) had put a time frame on their offer.... Of course they said no, so I politely suggested that they should ring the REA and say that the offer stands for the rest of the day.... the house was theirs with no counter-offer straight away.

Unfortunately they may try and get another offer out of a slightly interested party or the REA is unsure themselves of whether the offer is good, especially if it is below what the REA said that 'the property was worth'.
GL