Thanks for your patience here. This feature is now live and has been implemented.
We've exposed the delivery address details for use on a PDF theme.
The full details on the change made is available at http://www.kashflow.com/change-log/delivery-address-on-invoice/ and full documentation is available at http://www.kashflow.com/akademy/kb/delivery-address-on-invoices/
We'll probably look at simplifying this functionality later on in the new version of the application.
Thanks again for your feedback here.