Help with tenancy set up

Tax Planning and Financial

Hi myself and partner are about to become landlord and lady of a flat that we have purchased... there is no morgage on this property. We do not live there but purchased it for an investment. We want to manage our own tenancy and wish to set this up on a six month short term tenancy using one of your tenancy agreement packs. Firstly if it is a short term tenancy when do you proceed to ask the tenant to leave ? two months prior? Secondly if the tenant is stable and we are happy when do we produce the next six month tenancy? And finally it is up to the tenant to pay all bills whos responsible if they leave their utility bills unpaid?
Thank you
jan