Find out as much information as you can about the current financial position.
You have the right to view the documentation for your building. Make an appointment with your agent to see invoices, bank statements and the present balance for the current financial year.
Make copies or notes of who all the contractors are, which bank your funds are with and the account details. Ask to see a copy of any contract your company has with the agent. Make a note of any notice period or termination fees.
Ask for a schedule of arrears. They will probably only give this to the directors.
Now it's time to start looking for new agents. An organization called LEASE publish advice on this but here are some pointers.
Go to step 4.