A shorthold assured tenancy which this will probably be if created after February 1997, it has to be for a minimum of 6 months, some landlords give notice with the start of the tenancy to enable them to ask the tenant to leave as soon as the fixed part of the tenancy has been served. If this is not the case and they do not leave after the fixed part of the tenancy has been served it will become a periodic tenancy and the notice will then be as coffee states 2 months written notice in a proscribed form by the landlord 1 month by the tenant.
There is virtually no security for the tenant after the fixed period of no less than 6 months.