If the vehicle is not fit for purpose and you have given the supplying dealear time to recify the faults, there should be no termination fee involved and espicially one of £250, as the car is a dud one.
I expect the person you soke to gt things wrong, so I would be emailing the CEO and pointing out you want to reject the car because Peugeot has had enough time to fix it and as its not seen as an early termination, you don’t see why you should be charged £250.