My DMum was told the wait was 12 hours a few months ago. I was there waiting with her, thankfully they then phoned and triaged and made her a priority and it was only a few hours in the end. She had broken her hip and there was no way we could have got her downstairs.
A few years ago we waited three hours then were told it would be longer so 5 of us managed to get the casualty in the car, typically just as the ambulance turned up. They said to take him in the car as it would be too painful to move him again.