Hi Paul
Should be an easy fix mate. The light your seeing on dash is "door open", not door unlocked. When the light comes on, are the doors actually open when you check them? If the doors are closed, then the problem is an easy fix. If you open the doors, you will see a small microswitch on the C pillar near the catch. It may just need adjusting. Undo to screw slightly just enough to let you move the switch. Move it outwards (away from the car's interior) then retighten. If the problem persists, try spraying a small amount of WD40 into the switch them work the switch in and out. If that doesn't fix it, replace the switch.
Let us know how you get on.
@pau2112