I've just had a new key cut as the other one snapped but it has now caused some problems.

 

The key turns ok and the engine starts but when I turn it off and the key all the way back most times all the ignition lights stay on. It then take 5-8 times of turning it back on and off again until they go out. I can even take the key out of the ignition and all the lights are still on! Is this just because the key is crap and I need another one done?

Sounds like a dodgy key mate not making contact with the tumblers properly

sounds more like the ignition !

When I had a key cut locally it also worked but had some strange 'side effects'. On comparing the old with the new, I noticed that the grooves that go the full length of the key were a slightly different width. I have now bought some genuine Nissan blanks and will get them cut accordingly.

key problem i had exactly the same symptoms with mine ....cure as above Nissan blank and get that cut.........no problem