I have checked my head unit and it say GD-01 so can assume that a camera will not work??????
Correct. The GD-01 head-unit doesn't have a camera input/connections.
Out of the following couple of options - the one crayman has done is probably the: cheapest, easiest and quickest. But look less 'stock' - having said that you might be able to get a nav unit with input for a reverse camera (e.g. NAVMAN MYEscape III).
So basically there are three main options:
1) As crayman has done, and others suggested/did, fit aftermarket camera and screen. Or:
2) Get a GD-02 head-unit (which could be hit or miss on ebay - often people are listing these types of head-units as 'i30 2012+ ....' or 'i30 GD....' instead of GD-01 or GD-02) and wire a camera to it - this could be further complicated if the head-unit plug(s) doesn't have those connectors/wires. Also if an aftermarket camera is used in this manner you would have to work out/check which connections/voltages are needed to operate. If using the OEM badge camera (not cheap) this would be less of an issue - but you would probably need to make the hole required to mount it, and you might still need to run your own wiring.
3) Fit an aftermarket head-unit (with camera input) instead of a GD-02 and wire a camera to it - the lack of connections on the plug for head-unit issue will, likely, be less a factor (as the unit will probably require different plugs to be wired).