This would be an unexcused absence and is likely grounds for dismissal.
With respect to them refusing, they have right of refusal so long as they do it minimum 2 days in advance.
- Booking time off
The general notice period for taking leave is at least twice as long
as the amount of leave a worker wants to take (eg 2 days’ notice for 1
day’s leave), unless the contract says something different.
An employer can refuse a leave request but they must give as much
notice as the amount of leave requested, eg 2 weeks’ notice if the
leave requested was 2 weeks.