I went through the same in April 2017. I was in the fortunate position where I was about to get my full RAF pension ( and a wife with a very good salary who is a key worker as well ?) I was able to use the transition payment to buy a nearly new car on PCP. I also expected I would win my appeal, so the PiP money would come back.
This was the second time it happened to me though. The first time I wasn’t in such a good position with the kids all being young, I just had to make do with whatever I could get, that time it was a serious error by the doctor who examined me and I only had to wait a few weeks to get my award again but it was still too long a time to keep the Motability car.