Posession

Tenancy Types and Management

My tenant is 4 months in arrears and has also breached the AST by moving her brother into the flat without my permission. She tells me she has lost her job and cannot afford to pay the rent. She has been to the houding benefits people who tell her that she can stay in my flat until i issue an eviction notice and only at that point will they find her somewhere else to live?
The tennancy ends on 16/06/07 what is the best thing for me to do? I have been advised to issue court proceedings or wait until 17/06/07 and issue a accelerated posession order - but i just dont know? and how do i go about getting the unpaid rent back?