Short or Long Let Available for Double Room

I am the current tenant of the house and have a large double bedroom on offer.
I am moving out of the house a month early, therefore I am looking for somebody to replace me for the remaining 4 weeks of my tenancy with the opportunity to continue the tenancy for a further 12 months when the contract is renewed on 1st Sept.
The current 4 housemates are also leaving at the end of August, so there is potentially another 3 doubles and 1 single to be filled.
The deposit is dependant on the length of stay, if it is a short let I would ask for 1 weeks rent, however if you are looking for the long let of 13 months then the deposit of £520 will be required.
It is a large double room, fully furnished. There is a shared living room, kitchen and bathroom all of which are in good condition.
Please let me know if you have any other questions regarding the room.