DD has an application in for accommodation at her insurance offer, but they won't process it unless/until she firmly across her offer. So she almost certainly won't get her first preference but they do guarantee to allocate university accommodation. That is by no means the case everywhere and was a factor in her choosing this university as insurance.
At this stage, I guess all you can do is make sure he knows the system and is ready to spring into action as soon as it becomes necessary (if it does). And potentially research private accommodation options in Leeds now so that you know what the fall back is as can act on it if necessary.