Abuse is a strong word and I only use it because it’s the word which Motability uses in it’s terms. The unfortunate fact is that what you do/are proposing to do DOES qualify as abuse of the system as the vehicle is supposed to be used solely for the benefit of the PIP/DLA recipient, and not for the personal convenience of anyone else for any reason. The terms may seem harsh and unbending but technically you’re not only breaking the terms of the lease, as someone else already mentioned, it could be argued that you’re also illegally evading road tax.
I know you’re new here so may not be used to my habit of looking at all sides of something, please don’t take this as accusatory or judgemental, it is 100% about my interpretation of the rules as they stand and not, in any way meant to be personal, I promise.
"Man is born in freedom, but he soon becomes a slave, in cages of convention, from the cradle, to the grave."