I think in most cases it's not the building space, but the staff.
If you put a teacher and TA, for instance, in a church hall, are either of them first aid trained? How is the building cleaned? How are the children walked from the church hall to wherever they have their lunch?
Teachers are still waiting to hear what the mystery summer holiday provision will be. And will no doubt her at the same time as parents.
The government have really frigged it all up.