But it appears as though without hitting that 'confirm and pay' button the purchase is not recorded with eBay.

I am trying to have the purchase recorded - but not payment in full.

The idea was once the buyer 'purchased' the item, I would then let them know how to send me part payments. EBay gets their FVF, we have a record of the transaction and I get their contact details (such as they are). If the buyer then reneges on payments I still have the article.