I was commissioning a new phone system for a customer and as part of the process we are required to test 000 or 112. Pretty easy, called the number gave then the approved speel of this is only a test call for a new phone system and asked them to tell me what number I was presenting.
Never had to call because of an actual problem.
I just wrote up a small letter saying that I will be leaving and my last day of work will be X day.
If they as questions I do answer them but don't go into detail.