It could be a clutch problem or the linkage and selector plate.

Can you select gears with the engine stopped, or is it only when the engine is running that you see this problem. If you can find all gears with the engine idle then it looks like clutch drag. If it makes no difference whether the engine's running or not then it could be corrosion in the linkage between the gear stick and the gearbox, or the selector plate. You will find quite a few threads on the forum about this.

Hope you get it sorted.

 

It's not selcting no gear when the engine is running or not. 3rd gear can only be selected sometimes!... it could be anything really. But i did notice the "low warining oil" light appear once. prior to the problem i haved topped my oil up coz it was low..
I could'nt tell if it's leaked oil, coz it has been raining...
Also two weeks ago the car wouldnt go in to 4th gear? i thought that could of been due to swarf...