Hi Laura,
I was in the same position as you last year, with similar physical needs and requirements of my next car through Motability. Up until January of this year, I had an Audi Q3 that would have been 6 years old next month. I would have been happy to keep it even longer but Motability told me that I needed to choose another car fast as they needed my car back asap or I would have to consider leaving the scheme (temporarily) as the wanted must back.
I ended up choosing a BMW X1, which is a lovely car but doesn’t have everything I needed as standard. A reverse camera and park assist would have made my life so much easier and more comfortable but wasn’t standard or able to be added due to the global chip shortage. (I’ve had a right-sided stroke and osteoarthritis in my neck, hips and knees.) I know that if I continue to struggle, I will be asking to change my car when other more suitable ones start to reappear on the scheme.
I guess all you can do is possibly swap or cancel your order and try to hang on if they’ll let you? I know that the car choice is even worse than when I ordered mine last year in August. Good luck!