If your deposit has been registered with one of the three schemes, you would have received verification in the form of a certificate or such. Also, this would have had to be included as required information on your tenancy agreement. You need to check thoroughly - search on the internet typing in Tenancy Deposit Protection Scheme and this will give you all the information you require.

Hi As your Tenancy originally began before April 2007 it will be classed as continuous from the date you first took occupancy and would not therefore need to be registered under the new scheme. However, you could possibly put the agent on the spot and say any new Tenancies issued after 6th April 2007 should by law include details of where the Deposit has been registered and ask why this was not included - assuming yours does not. Basically, your agent cannot withhold your deposit, if they cannot prove the condition of the property at the time you took possession. If you contact the Ombudsman of Estate Agents (which every agent should be registered with) they will give you all the support you need.