Ok - then you can't take action on the tenancy.
You may be able to take action in terms of mud, but normally that you can only seek an injunction on nuisance.
That is noise, smells etc, deposit.
You could argue it was a deposit/
Therefore on that basis you could seek an injunction
Clearly they would need a Solicitor to draft proceedings and represent/
But this is a statutory nuisance and they can seek an injunction
Can I clarify anything for you?
For more info please see: https://www.gov.uk/statutory-nuisance