Bazza:
If he has been given a deposit as OA has said as £500. then he has accepted this as a sale at the price agreed and with a deposit agreed.
If he wanted to hold out for £1K he should have done so - so he has negated the small print...by accepting monies for sale of an Item...
But OA my gut just says that you asked to see more details and photo's etc...
Perhaps this has spooked him - for what reason you need to ask yourself
Chris