My wife terminated a Mokka in 2013 after 3 months due to a number of issues including seats that caused pain.
There was no fee for that but you don’t get the Good Condition Bonus, which is only fair.
The AP was returned pro rata, i.e. less the months of use we had, but just be aware, we had to run the Mokka whilst we found a replacement car. We had to pay the AP for the replacement car on delivery, and only then was the initial pro-rata’d AP returned to us once the Mokka had been returned through the second dealer.
So we basically had to put the second AP on a credit card.
Motability will advise on the options but just keep our experience in mind so that if it does play out like ours did, then it won’t come as a surprise.