I don't have a blue badge, but suffer badly with arthritus in the knees and feet and have bad circulation in my legs.
My big gripe, is that car park spaces are always too narrow. I am not allowed to park in disability parking bays. However the worst nightmare is when people park so close to your car, that you can't get into the car from the drivers side. That didn't used to be a problem, when I was able to climb in the passenger side and crawl over into the drivers seat. Unfortunately I am not able to do that anymore. So when it happens, I have to wait until the person who parked next to me comes back to their car.