Now I remember you. You had an issue with your seatbelt. When a Fiesta starts having electrical gremlins like you've been having, you should check the battery.
It may have enough juice to start the car, but that doesn't mean it's working properly. Most places that sell batteries will test yours for free (at least they do here in the US).
A lot of people report weird electrical bugaboos, then they replace the battery and it goes back to normal.