Ask a Family Law Question, Get an Answer ASAP!
Firstly she can leave the house with the children if she so decides. She has no greater call to the children then you and as such you could make an application to the court for a child arrangement order so that the children live with you. You should advise the council that you still want to live in the property, although if it is a joint property she can revoke the tenancy.
You should go to mediation unless you both agree not to do so. Then you can apply for a child arrangement order. I would advise the housing association that you need the property for the children to live/stay with you.
You can make an urgent application for a child arrangement order yourself should you want the children to live with you. I imagine if you go to take the children the likelihood is that she will contact the police and make things difficult.