May I ask if your holiday involved travelling by car? Whenever I am a passenger in a car for long periods, more than about an hour, and especially the four/five hour journeys to and from university, my readings become an absolute mess. I don't know why, but every single time, without fail, it happens.
And I would say from my experience that stress definitely seems to raise blood glucose levels. Every year, during exam season, without fail, it will be significantly higher, irrespective of activity or diet, which doesn't really change.