is this legal?

I have made an offer to rent a flat. Agent asked me for deposit to take it of the market.

My income isn't great but I can afford the place, it has been 2 days Indiantown hear from the agent.

He said landlord will decide in a day or two. They don't reject or accept the offer although they reduce the property price by £3

If I pull out and look for another flat I will lose my £400 deposit.

Is there anything I can do?