Address Lookup form; not taking 'Delivery Type' into account when automatically populating postcode

The Address Lookup form (viewed by clicking the edit icon next to an address) was not automatically populating the postcode when it had enough information to do so.

This would occur if multiple postcodes were available for (in Australia), the Suburb, State combination (viewable by clicking the lookup button next to the postcode form). The available postcodes list did not take into account the 'Delivery Type' that could be entered at the top of the form, therefore the list may have contained two postcodes, one for a PO Box and one for a normal delivery area.