Why go to the hassle of swapping them? Do they remaining units have different lease end dates?507003 is at Southport now ECS from New Brighton so presumably 507018 carried passengers for the last time this morning.
Edit: Indeed the case. 018 is done; it is about to leave Southport ECS for the last time. I'm glad to have made the effort to ride it this morning. A superb unit which will be sorely missed.
