Implement a non-working day calendar, primarily to make case reporting easier
A non-working day calendar would automatically have weekends and UK bank holidays marked as non-working days. Each day in the calendar would have a flag with suitable values. Something along the lines of 0 - (working day), 1 - weekend (non-working day), 2 - public holiday (non working day). When you create a case report you can easily exclude working days by using a criteria that says "working day = 0".