Negotiating return of deposits prior to the TDS

Tenancy Deposits

I have a property which was occupied until recently, the agreement commenced on 06/01/2007. I need to dispute the deposit return with the old tenant, my initial problems are:
The original letting agent is being very unhelpful and I'm not sure what scheme the deposit is held under. They originally stated that the deposit had been transferred into the TDS, is this possible?
The old tenant will not communicate or negotiate with me.
I am at a loss to know whether I need to go through the courts to recover my loss or where to go.