In most circumstances, the copyright in any photograph commissioned by UOW (after 30 July 1998) will be owned by the photographer, unless UOW and the photographer agree otherwise.
You will need to weigh up the benefits of owning copyright in the photographs, against the potential extra cost involved in obtaining copyright.
One option is to purchase a licence from the photographer to exercise all or some of the copyrights in the photograph for a limited period of time, purposes, and/or uses. From UOW's point of view, this option is much less flexible than owning copyright, and consequently you will need to consider all current and potential future uses for the photograph before entering into such an agreement.
You may agree to either an exclusive or non-exclusive licence. Under a non-exclusive licence the photographer will be entitled to use the photographs as they see fit, unless UOW obtains the photographer's agreement only to use the photographs in accordance with the terms of the agreement.
If appropriate, you should seek legal advice to ensure that the agreement covers UOW's needs and is enforceable.