So now you tell us that it is a car park with separate in and outs? That clarifies the situation a little.
All I (and others) had to go on was an aireal photograph of part of a car park, so I assumed that the entrance/exit pictured is in fact an entrance/exit. I therefore stand by what i posted before.
However, if as I assume, this car park has separate entrances and exits, and you were going towards the exit pictured, then I would say that the other driver is at fault.
You have stated that he hit you rear end passenger side, therefore you were well in to the junction before the collision, and he shold have been able to stop.
If he hit you that hard that he spun you car around, and caused it to be a write off, he must have bbeen going some considerable speed, not appropriate to the car park.
Hopefully this is of help to you now.
I try to be helpful, but if you do not post all of the facts, then how can you accuse others of not trying to help. Thanks.