Council Tax Citizen Arrest

In January 2013 I was being pursued for council tax arrears from a different council to the one I was then covered by. I was told I needed to attend court and I explained I had a mental illness and would not be able to .The gentleman said I would need a letter from my GP but never believed I had a mental illness. I have bipolar PTSD and GAD. I am in receipt of ESA and get the severe disability supplement and receive the enhanced rate of PIP. To try and keep things short , I was on the way to my GP to collect the letter and the Councils agent (a court officer I think ) physically restrained me by holding me by both arms by my bicepts.Whilst holding me I was able to call on loud speaker on my phone , my GP who read out the letter so the gentleman could hear the call giving my diagnosis and the several medications I was on and saying currently I was not well enough to attend court (I still have that letter) The police arrived took me to the GP where I collected the letter was taken back to my street and told by the police to go back inside my house . I heard nothing from the council there after but they did deduct money from my benefits .I have recently realised that I may be exempt from council tax due to severe mental illness which I have been diagnosed with for over 20 years .How should I proceed ?