If I have assumed correctly, you have a possession order from the court for Monday 30/11/23 against an S21 which has been through the court process. In this case, if your tenant has not moved out, apply immediately for a “Warrant of Execution” for the bailiffs to physically evict the tenant.
It depends where you are and how much of a backlog the bailiffs have as to how long you will have to wait to get them out.
Advise the tenants what you are doing and that they will be physically evicted, unceremoniously, if they do not move beforehand, it may just encourage them and the council to move their backsides before that event.