Sorry. hadn't read the bit about closing anyway. I agree. If you are not giving your staff the option of working and have not agreed this beforehand you should give them a goodwill day
Legally the employer can decide when annual leave is taken. However, given the short notice, it's not very nice to force them to take it as annual leave. Many employers give it as a goodwill day.
We take it every year as a days annual leave. At the beginning of the year all the staff and management get together and decide what days we will close for annual leave.
We also take the day before or after St Patricks Day depending on when it falls. We close for the first 2.5 weeks in August from the bank holiday weekend every year without change and for 2 weeks again at christmas.