Agree with Wardy, you should have checked before putting entering your PIN or at the very least spoken to dealer and Motability, as soon as you came across the paperwork when you got home. Delaying contacting imo may proove exceptence.
I would without delay email the CEO, explaining the situation and that your not happy that the supplying dealer did not make you aware of this when collecting and you have overpaid by £700 for a lesser model your not happy with and what you would like the outcome to be. andrewmiller@motabilityoperations.co.uk