As a parent I have total empathy with the child seperated from parent experience described here.
F3G is right it is a CAA "guidline" that all airlines implement procedures to ensure children are seated with the accompanying adult. It would be a foolish airline that would actively ignore the CAA (not saying that was the case here just wanted to give parents a bit of extra ammo
The CAA go so far as to state how far a child can be seperated on both wide and narrow bodied jets. I expect this was a 73/757 so this would be one seat row.
However it is Jet2's policy that all children under the age of 14 have to be accompanied by an adult 16 or over who will take responsibility for them. Furthermore I don't belive any airline is allowed to ask another adult to take responsibility for a child. I could stand corrected here.
This little girl was only 3 years old yet expected to sit unaccompanied 2 rows away from her parents who are responsible for her.....unbelievable!! She would be frightened at being separated from her parents in a strange enviroment, need help with food and drink etc.
Parents you should find the CC of any company proactive in sorting this situation out but if not just ask politely who will be taking responsibility for the little one in the event of a decompression, turbulence or an emergency situation......you will soon get moved together!!! The CAA guidlines are in the interests of ensuring safety in these events.
Hope this helps