You get the deposit back unless in the rarest Off cases they gave you in writing the full conditions of such deposit and it’s clearly stated the deposit is none returnable, No dealership can take Any deposit towards the AP or anything to do with Motability, Any payment they took is either towards Options/extras and-or a holding deposit so unless they gave you details term from thier dealership (nothing to do with Motability) and any conditions then they have to give you a full refund of any payments made.
If they say motability said No to a reduction as been mentioned above they are trying it on once you say “Ok I’d like to cancel” they will change their mind and make out they are doing you a one off favour and bending the rules for you, once they’ve made you feel so lucky and how privileged you are and agreed to the lower Ap (get this in Writing/Email) then they simply spend 30 seconds and change it on the back office system. How wonderful of them.