return of deposit ?

Tenancy Deposits

I initially let my house using a letting agent. They carried out an inventory at the start of the tenancy.
Due to various problem , I dis-instructed them after 12 months, we have finally managed to get our tenants evicted a further 5 months later, they leave on Wednesday.
The agent says that as they were dis-instructed they will not be carrying out a final inspection.
We have not managed to see the property for many months but know that there is likely to be considerable damage done by the tenants.He has approached the agents to ask for the return of his deposit.
They say that we should open an account with the DPS and they will transfer the deposit.
How do we agree on the costs of any damage, is it possible to claim back any of our considerable legal costs of evicting him.
Should we insist that the agents carry out a final inspection, otherwise it is our word against his ( we could take photos of the damage )