It depends how much paid holiday your staff currently get.
For a standard 5 day week, they are entittled to 24 days paid per year. This includes all bank holidays and public holidays.
If they don't currently get this, you will have to allow them the extra paid holidays. If they do have this much already there is no extra entitlement until 1st April 2009, when the entitlement increases to 28 days.