You can't go wrong with a switch that breaks (disconnects) both 220V wires. You might also wish to put a fuse inside your case. Theoretically if you keep all the 220V wires isolated breaking both lines is not needed but it won't hurt.
When wiring your project you need to be sure any 220V connections and anything that gets hot is not directly against the wood. If the power supply needs cooling air you might have to put some openings in the case (perhaps covered with a screen or perforated aluminum).
When you start to layout the case make a special effort to keep the 220V wires / switches / fuse as far away from the power supply output and low voltage wiring as possible. You should have high voltage on one side and low voltage on the other side.
You might want to look for a "chassis power receptacle with switch" I've seen them for the US plugs. They contain a power cord receptacle, a fuse and a switch in one housing (meant to be chassis mounted).
i looked for the 14ga pigtail on google and i see it is a cable with a screw on one side. if i screw it on the wooden case, will it work as a ground?
No, wood does not conduct electricity (except when its wet). And from your description you don't have the 3rd wire "equipment" ground (which in the US would be connected to a metal case/chassis etc. Your best bet is to keep all the 220V wiring isolated as much as possible. Neither 220v wires should be connected to anything except the power supply input, the switch, a fuse and of course the incoming power cable.
Good luck with your project.