Rent inclusive of council tax?

Most renters do not pay taxes the landlord pays the tax and it is part of your rent. However, in your situation the landlord may have a illegal duplex. The real question is, is the unit safe, duplexes are normally required to have dire walls and fire rated doors. Check with your local housing authority to determine, it could save your life one day. Bu if the govt finds the landlord or tells him he can not rent as a duplex one of the tenants will have to move.