I think it depends on the case manager you get.
You can say what the car needs to have as standard, so some base models may not have certain things e.g. lumbar support, heated seats etc so if you were looking at the next level of base model that you could say it’s because of those things etc.
But usually they give you a list of cars, I been going through grant process from September. Finally got granted an AP for a small SUV as original caseworker only granted me for a large SUV.
My new caseworker was happy keeping the same grant amount i was awarded for a small suv.
It’s means tested and I believe they do fund adaptions also