Delaying payment from a Buyer

A buyer has purchased two items which are now due for payment.

They are bidding on a third item and I am happy to delay payment of the first two  until bidding is over for the third item.

If they are successful at bidding this will enable payment by one invoice and postage of all three items together.

Is this possible?

Yes...send a combined invoice once they're finished....if they beat you to it, refund the difference

As above,  but if you have your preferences setup to automatically cancel unpaid items,  you need to turn that off if you have it set for before the last items finishes.