anti social behaviour section 8

Possession - Section 8 and Section 21

Hi I have a tenant with a rolling tenancy agreement. Been in situ 6 years. Over the last 2 years there have been numerous issues with ASB plus extensive damage to the property, which currently has a back door that has no glass or lock, the tenant damaged both. No glass in the back downstairs windows of the property due to damage by the tenant, police attended, we boarded up. No glass in the front bedroom window, damaged by tenant, police attended. The front door is now secured by a haspen staple type lock as it has been drilled out so many times (by ourselves and police) to replace it it is now none functioning. The door panel has also had to be replaced as that was kicked through by someone known to the tenant. The front door has also recently been kicked through again and again police attended. I have told the police I wish to proceed for criminal damage and been told it would be thrown out due to the tenants "mental health issues". I have a log of numerous complaints from neighbours so have a log of about in total 15 issues over the past year. I am in a position to proceed with a Section 8 as I have told that it is very difficult to prove ASB in court. I have also applied to the police under the freedom of information act for information (ie incident log nos etc) to further add to the my log/ evidence. The neighbours seem to think the house is being used for illegal activity as it is quiet for perhaps a week then dozens of people on bikes and in cars will turn up over the period of 1 night almost as though it is used as a distribution centre.
I have until recently been trying to stop the ASB by liasing with the tenant, social services, police and her family all to no avail as the tenant seems on a downward trajectory.
To make matters worse, due to the tenant signing her children over to the care of social services she has had to reapply for U.C and as a result there are now arrears of (currently ) 2 months. I have applied to U.C to have the arrears deducted from her claim and to come directly to me.
I feel I have done everything I can to help the tenant and stop the ASB and this situation cannot continue.
That's the back story.
Question 1. Do I have sufficient grounds for a Section 8
Question 2. In the current circumstances how long will it take (roughly) to go through court and gain possession?
Question 3. what is the best way to proceed