Martin mobility are good when it comes to a vehicle not suitable for your needs. They even waived the 250 fee for me.
Best thing you could do is try a and find a suitable stock car are you will be stuck with the current car for between 6 months to a year waiting on a new build car.
Remember even an extended test drive will never be close to having and using the car everyday.
My first car was returned after about 3 months due to not being able to use the clutch. The only thing they were fussy about is whether you had a test drive which you did. Also I would just stick to the ‘now not suitable for my disability’ excuse and say nothing about the other stuff. GL