Final payslip and think I might get rinsed on tax :(

Fyi I’m 23 and leaving my job soon. I earn £23k a year but this final payslip coming up will include 18 days of holiday pay I didn’t take (don’t blame me, I really needed the money). I work 9–5 with a 1-hour unpaid lunch, so 7 paid hours a day.

Normally I earn about £1.9k before tax and take home around £1.6k. I reckon this final payslip should be about £3,200 before deductions. From my rough maths, I might end up with £2.2–2.3k after tax and NI which is disgusting. However does that sound about right? If so, I’ve made a huge mistake and should’ve just taken the holidays ffs.