Drangonfly your quite right some dealers will push and want it for end of years sales figures. But with that in mind if the dealerships figures are good they will be willing to delay, but officially you need to let both dealership and Motability know, the dealership can update the back office system for your continued use of present vehicle but may need you to confirm to Motability the delay is your doing to stop them getting fined. It shouldn’t be an issue just a couple of calls and you can relax.