Redundancy and Annual Leave - Who is correct?

Hi all,

I was recently made redundant. 

For years, I was paid a shift allowance of 33% of my basic pay for working night-shift/Saturdays. 

I barely took any annual leave in 2023 and finished with the company with around 25 days annual leave outstanding. They have paid for the 25 days, but only at my basic rate, so not including the shift allowance.

I've queried with my payroll asking if they forgot my shift-allowance but they stated that they only pay basic rate for annual leave.

Not sure if it's worth pursuing but a quick Google brings up the Organisation of Working Time Act, 1997, section 23 (Compensation on cesser of employment) states "the employee shall, as compensation for the loss of that annual leave, be paid by his or her employer an amount equal to the pay, calculated at the normal weekly rate or, as the case may be, at a rate proportionate to the normal weekly rate, that he or she would have received had he or she been granted that annual leave."

My argument is that the shift-allowance is part of my "normal weekly pay" as I've been on it for years. 

Their argument is that "normal weekly pay" means basic pay only. 

Who is correct?