Abandonment

Rent Arrears

We have a tenant who was having housing benefit. This was then cut in half recently due to benefit caps. I wrote to her explaining that she would need to find the extra money or seek some advice otherwise we would need to serve notice on her. (Has always been in arrrears so we were paid directly by the council).
I do not hear back from her and after a month or so and one month of only recieving half the rent we hget a letter from the benefit office to say that they have now cancelled her benetif. On finding out why from the council they told us that they believed she was no longer at the property.
She is not contactable and does not reply to letters.
After waiting a week my husband went to view the property and found it empty but with loads of studd still in it including clothes.
Any advice what to do next? We have also just had a letter from the council tax authorities charging us from 8th September onwards.
Thank you for any advice