I have had the same fight with the council with them refusing any retail relief. I do however not sell cars, we are just garage repairs and serving.
I have a rateable value of £26000.
In my correspondence with he council they would not even tell me why I was not retail, just that I was industrial and I should except that.
After quite a bit of research I managed to find out that it might be because of the B2 planning codes, but never got it confirmed.
I did however find a dozen or so councils that are including vehicle repair workshops in their retail relief scheme, so it will depend on where your business is located.
With the current crises it is even more of a blow as we will not be entitled to the free rates for a year, or any of the grant money announced.