Tenancy surrender

I signed the contract and paid the holding deposit and my tenancy starts On Aug 15th.Unfortunately my situation changed and i have requested tenancy surrender.But landlord is not accepting and demands 350 pounds on top of the holding deposit.Its been only 10 days i have signed the contract and requested surrendering on 11th day.I do t want the holding deposit back.Am i obliged to pay 350 on top of holding deposit.Please help

If you have signed a contract, you are legally bound to follow it

If you are breaching your contract, you are liable for the Landlords costs for the breach. The Landlord must be fair & recover only their actual costs, which could include more advertising, referencing of new tenants, lost rent as a result of the delay, costs for carrying out new viewings etc,