Is this a rented room in a house shared with your landlord?
OK. What was the contract that you were on?
Was this a shared house?
Did you have an AST?
What type of contract do you think you are on?
Ok. Did you leave in April?
did you give notice of no less than one month?
Then you are entitled to your deposit back unless there are arrears or damage.
If they do not provide it though then your only option is to sue.
This is not an AST so there is no immediate obligation to secure your deposit in a scheme but that doesn't mean they cannot just keep hold of it.
You can always sue at the small claims court but write to them first making threats of legal action. A letter before action will protect you from costs.
Can I clarify anything for you?
You do have the address of the landlord on the contract I think?
Is there an address for either?
There should be as you need an address for exactly these purposes.
No, you need to write to them first.
Yes, you can send it to the agents.
I would send it to both.
Then you issue against them at the small claims court.