Tenancy Deposit & arrears

Tenancy Deposits

I increased the rent last January of which the tenant agreed to pay. He missed the rent for April 08,After phoning him and listerning to his excuses he agreed to pay the arreas in 2 installments over the next 2 months of which i have only recevied the 1 payment.
I have phoned him several times since but only get more excuses.I did have an agent letting the property for me but had to sack him as he was always paying me late some times up to 2 months late.
I informed the tenant and asked him to pay me direct of which he agreed and has done so on time eversince apart from this 1 months payment.

He is saying that he has tried to get his deposit back from the agent and is having no luck doing so.

He is a good tenant and i don't want to rock the boat to much, he is due a new tenancy agreement in January can you help ?.