On Friday, 25 November 2016 10:06:51 UTC, WeeBob wrote:
On the back of the box, there are a couple of holes (extending from the
lid screws) which I can imagine would be part of a mounting system...

They're either part of the manufacturing process, or to allow boxes to be stacked on top of one another.

If you do need to fix it to the wall, drill through and use a round- or pan-head screw with a washer, or a flanged screw.

Owain