Are Cherwell District Council providing outsourced tax collection services to other Councils? According to their website they "also collect Council Tax for other councils."
Given so many Council's have massive Council Tax arrears perhaps this isn't actually a bad thing if it is as it seems. Why not outsoruce the job to another more effective Council? Sure it might cost you a little but if it's costing less than recovered arrears then maybe it;s a price worth paying?