CAST(REPLACE(o.order_ref, 'PO', '') AS UNSIGNED) AS Order_Reference, ...
WHEN COUNT(CASE WHEN i.status = 'Paid' THEN 1 END) = COUNT(i.invoice_ref) THEN 'No Action' WHEN COUNT(CASE WHEN i.status = 'Pending' THEN 1 END) > 0 THEN 'To follow up' GROUP BY s.town_village, ...