Two additions: That power supply has a metal housing. The fact that you cannot connect protective earth, as it seems, makes that potentially dangerous. You should act as if the case was under power. I am not sure how your country deals with this in general.
I think nobody mentioned strain relief yet. You have to make sure that your power cable is tightly connected in the box, not only soldered a screwed in. Imagine you trip over the wire, then it has to be impossible that the cable connections comes loose and dangle around in your device, or potentially even worse, the cable comes out completely and you have blank, hot cables lying around in your house.