Find the fuse box. It is usually located under the dashboard, on the driver's side.
Open the fuse box and locate the fuse for the interior light.
Check to make sure that the fuse is not blown. If it is blown, replace it with a new fuse.
If the fuse is not blown, then you will need to check the wiring. Look for any loose or damaged wires, and repair or reconnect them.
Once you have checked the wiring, turn on the interior light. If it still does not work, then you will need to take your car to a mechanic for further diagnosis.
Here are some additional tips for fixing a Vauxhall Corsa interior light that is on permamently:
Make sure that all of the doors are closed properly.
Check the dimmer switch. If it is turned all the way down, the interior light will not come on.
Try turning the light on and off a few times. This may help to fix a stuck switch.
If you have a sunroof, make sure that it is closed properly.
If none of these solutions work, then you will need to take your car to a mechanic for further diagnosis.