If you have signed a fixed term contract and you want to leave early you will only be able to do so if there is a break clause in your contract or the landlord agrees to you ending the contract early. If your landlord does agree to end your contract early you will need to make sure you get this in writing, just in case there is a dispute later. The landlord is under no obligation to agree to end the contract early, they can insist that you pay the rent for the remainder of the contract. If you leave the property without the consent of your landlord you will still be liable to pay the rent for the fixed term.
You can read more about ending a fixed-term tenancy here.
When you move out of the property the landlord agent should check the condition of the property against the 'move-in' inventory. If the check-out inventory is scheduled to take place in your absence, make sure you carry out your own checks and photographs before you leave the property. It is the responsibility of the tenant to leave the property in the same state it was at the start, less wear and tear. If any repairs or cleaning are required this may be deducted from your deposit.
Call the utility companies to close your accounts, provide the final meter readings and pay any outstanding balance (or claim a refund if you are in credit).
For a small fee, you can ask Royal Mail to redirect your mail to your new address - you can read more here. To save time, register with I Am Moving and they will notify their database of companies of your change of address free of charge.
Your landlord should return your deposit once your tenancy agreement ends, less any agreed deductions for damage to the property, cleaning costs or unpaid rent. It is common for tenants and landlords to disagree about deductions from a tenants deposit once the tenancy has ended. Find out how to get your deposit back on the Shelter website here.
Clean the property
You should leave the property in the condition which you move in, less fair wear and tear. Therefore, you will need to make sure you clean the property to a good standard, otherwise, the landlord may use some of your deposit to have the property professionally cleaned.