BUT you have to remember that if, for instance, S Yorkshire don't join the national scheme - then the costs of South Yorks will fall just to South Yorkshire - and not be added to the national bill. So the 'members' making the contributions falls by one, but the overall total the remaining members have to raise is £1.67m less (according to this thread).
So what is the optimum number of authorites that need to
FULLY sign up to NPAS in order to make the greatest savings for the member authorities?
What if only one authority signed up....?