Earthing?

[manofgresley]

Hi again.

I need advice on earthing, generally I am ok, but being new to electronics I thought I would get a second opinion.
My question is this,my PSU, Drivers etc; are enclosed in a metal cabinet. I ordered an On/Off switch for the cabinet, it arrived with 2 poles only. The cabinet is powered from a 3 pin mains socket, can I use the earth cable of a 3 wire circuit, to earth the metal cabinet, by attaching the cable through a hole in the cabinet wall, and attaching with a bolt/screw?

This is what I have now.
Regards

Ray