An alternative (lieu day) holiday must:
be taken by the employee on a day that is agreed between the employer and employee
be a day that would otherwise be a working day for the employee
be a whole working day off work for the employee, regardless of the amount of time the employee actually worked on the public holiday.
not be taken on a public holiday
The alternative holiday can be taken at any time mutually agreeable to the employer and employee, and is paid at the employee's relevant daily pay, or average daily pay (where applicable), for the day taken off.
If an employer and employee cannot agree when an alternative holiday is to be taken, the employer may determine when it is to be taken.
So basically, yes but if you can't agree with your boss then tough titty, s/he can choose it for you