How do we make a smaller home workable for two sisters with different bedtimes?

At the viewing, our fifteen-year-old asked where she would study after her sister went to bed. I pointed to the kitchen table. My eleven-year-old asked where everyone would eat. The cheaper flat suddenly looked smaller than it had in the photographs.

We're considering moving from three bedrooms to two. In the budget we're working with, the move would reduce rent by £200 a month and put us nearer my work. The girls would share the larger bedroom. The older one does homework until about ten; the younger one prefers lights out at nine and likes building things on the floor.

My partner thinks a good storage system and separate beds would solve most of it. The older girl says storage doesn't give her a private place to change or finish work. The younger one says she's always described as the obstacle, although she didn't ask us to move either.

We haven't committed to this flat. What would be a fair way to test whether our proposed arrangement can work before we accept the saving? I want their concerns to affect the decision, even though neither child can be expected to solve the household budget.