The PIP mobility weekly amount is £75.75 or £328.25 per month and this is what you will be paying for your car once it arrives. So….you can save up that amount before you get your car in order to afford the AP.
That’s what I and countless others do. Sure I’d love to get a posh car with a £4k AP but I can’t afford anything like that. My last AP was £750 and the one before it £1k. That’s about my budget and it takes a fair bit of scrimping to save it up.