Normally yes you have to get grant authorised first but due to covid I was able to get one retrospectively. Thing is they will only allow for a vehicle class that suits your needs. I got a BMW x1 due to the height of it and the boot space is what I need, I called and they sent the form via email and I filled it and sent it back the case worker called back went through why I picked and needed that car eg. Automatic tailgate, big boot, folding mirrors, reversing camera , automatic etc they then asked if I got income related benefits showed proof of them then they called and informed they would give me a grant, the amount and the class of car. I then called the dealer and they done what they had to and it was all sorted and no delay on build. What BMW did you get? Is there a need for that particular model? The grants team are lovely so I would definitely give them a call.