This is an enclosure for covering the mains voltage and output connections of a standard 12V 300W fanless power supply such as can be readily purchased via eBay, for use with Ormerod 1 or other 3D printer. It has cutouts for a switched and fused mains inlet, 20A output connector, and indicator neon.
The parts that fit the holes in this enclosure are:
Power supply: 12V 300W regulated power supply, available from several eBay UK suppliers
Snap-in switched and fused IEC mains inlet: Maplin N94CZ
Mains neon: Maplin BK54J
20A Neutrik connector: I used Maplin N55GB with mating plug N54GB, but Maplin now sells the official "power out" version which is A52QQ with mating plug A48QQ, so I recommend those instead
A modification I suggest is to countersink the screw hole on the right hand side. Using a countersunk screw there allows you to stand the PSU on its side, taking up less desk space.
You can get IEC mains inlets that incorporate the neon as well as the switch and fuse, for example Bulgin BZH01/Z0000/02, is available from Farnell and elsewhere. Using one of these would simplify the mains wiring, but you would need to adjust the cutout size in my design. The Neutrik connector part numbers are NAC3MPB-1 with mating plug NAC3FCB, also available form Farnell.