Sorry to say but I don'tm think you have a leg to stand on.

They weren't selling you the car new so the warranty part doesn't really apply. They might do it for you as a goodwill gesture but there's no obligation as if it has previously been repaired than any paint/bodywork warranty is nul and void!

Trading standards won't be interested as the car is roadworthy and therefore it's not illegal for them to sell the car.
Hopefully as you paid a reasonable amount for the car, the dealer will want to keep you as a future customer and sort it but that maybe difficult if you've had the car for sometime. They may argue that it is you that's had the car sprayed!

My mate works is a paintless dent removal bloke and some of the horror stories he tells me of brand new cars at dealerships that have had bumps and scratches, tried to hide them, done a sh1te job and sold it to the customer hoping they don't notice when they take delivery.

BUYER BEWARE !!
