There should be a General Aviation supply store at the Sydney Airport.
Check with them for a "Dye Penetrant" crack detecting kit. it should be relatively inexpensive, and You tube should be able to show you how to use it.
its a three part system.
you spray the dye on, clean off the excess, then apply a spray on powder ( like talcum powder).
if there is a crack , the dye will have been absorbed into the crack, and then a thin line will show on the powder.