The deliver to location value is in iProcurement -> Preferences -> iProcurement Preferences -> Delivery
Metalink note 297757.1 (iProcurement Deliver-To Location LOV Defaults the Deliver To Org To The Item Master Org) states that the default deliver-to is set to be the master item inventory org.
If I have another inventory org set up, I can change it manually to that location code.
But I want to do it programmatically. Where is this value for the preference stored? I would like to change this.