Opal Corsa 1995, 1200, Ignition?

I have an opal Corsa 95, 1200, the trouble is with the ignition, the ignition lights will not turn off, you can even start the engine turn it off, take the keys out and it's still running. I have replaced the ignition switch, the battery and the alternator. the only way to turn it off is to remove the fuse and put it back, the ignition lights are then off, turn it on and you go through the same routine again to stop it

Please help

Thank You

Terry
February 2010