tiggytape I can see where you are coming from but one of the reasons the old system didn't work is because heads didn't want the confrontation.
no one does obviously want this in their work life. but when you manage people, you have to accept that saying no, sticking to it and it being unpleasant is part of life. Its not easy but heads were/are paid to do this. to tell people know and to deal with the fact that they will kick off about it. as long as the reasoning behind the no is sound and consistent then if the parents don't like it they can get their kids educated elsewhere.
it seems to me, from what you are saying, that heads supported the change because they really don't want to deal with the issues of consistency and confrontation. if that's the case, then that is very worrying. they are paid a decent enough salary to expect to have to deal with stroppy parents.
so what if someone asks for leave and is refused because their little darling misses a day a week. how is that unfair?
is the child who misses one day a week or who is late every day or tired or hungry any less disruptive than the one away for a week?
my reading of the situation now is that most heads can see that by bringing this in, their ability to use discretion has been eroded and that this makes them look more like the sort of "computer says no" head than someone in a profession . Initially it must have looked great, no need to explain the reason, just say the law is the law. but now of course it can be seen in the context of taking management away from heads and giving it to non teachers through the new legislation on academies.