2009 Ford Fiesta electrical fault

When I turned the ignition on today, I had an error on my radio display “Alarm triggered check vehicle”. There was no other error and no other warning and I couldn’t figure out what was wrong. An hour later when I turned on the ignition it was fine.
5 hours later (the middle of the night) the car alarm started going off. I unlocked the car and then locked it again but all the interior lights stayed switched on (including footwell, dashboard and radio display).
I’ve tried turning the ignition on and then the error message about the alarm came on again and this time it says the car boot is open. I’ve triple checked the boot, it’s definitely not open. I’ve checked all windows. I’ve tried locking the car again and the lights just will not go out - whether I lock the car with the fob or manually with the key.
Inevitably I will have a flat battery in the morning but has this happened to anyone else or does anyone have an idea of what the issue may be?