Retrieving tenancy deposit from letting agent

Tenancy Deposits

I used a letting agent to find and manage a tenant for me. The agent registered the deposit to 'my deposit' scheme and the money is held in the agent's account. The tenant has moved out from the property but unfortunately has also made some unauthorised alterations to the property.

The letting agent has agreed to get the property repaired. Although they mentioned that the cost will be covered by the deposit money, they seem very reluctant (and incompetent) in arranging the repairs.

I'm looking at the potential of having to arrange and pay the necessary repairs out of my own pocket, whilst the agent is holding all the deposit money that is in their account. Can you advise what is the best way to resolve this dispute?

I also want the property to go back in the market quickly. Am I right to think that since the tenant has moved out, I don't have any contract anymore with the letting agent; and therefore, can market the property using another agent?

Thank you.