Hi, I did try unplugging the freezer for about 15 minutes, hoping it would reset, sadly not. I do remember an engineer mentioning about pressing two of the front buttons, for about 3 seconds, and at the same time to reset, there are 3 buttons and I have tried different combinations of them but the flashing continues. Not sure what else I can try

Have you tried unplugging it for around 10 seconds and plugging it back in? That's basically the default way to reset any appliance.

The door of my freezer was left very slightly ajar, causing the temperature to raise to -2 and the alarm sound, however, the temperature has now reached its optimum of -18 but the temperature light and alarm light continually flash. I know there is a way to reset this but I can't remember how. Any assistance is greatly appreciated.