What's a decent time for someone to confirm a sale?

[SlowOne]

I advertised on here, got two expressions of interest within hours ( ). I do a strict 'first-come-first-served', no messing about playing one off against the other.

The first person has not gone further with their purchase for four days, and I wonder what people think is a decent interval to wait before going back to the other person. It has been over a weekend (people could be away) but we now have two working days and no reply.

What would a good Oopler do here? I'm looking for good, considered advice, so please try to avoid the vernacular and anything involving personal insults or injury!!! Thanks in advance Ooplers.