Hi Plek Trum,
For Person A, this leave could be influenced by section 222 of the Employment Rights Act 1996: as Person A worked variable hours between Jan & April, if leave was taken in this period (or the following 12 weeks), the calculations will be based on the average hours of the previous 12 weeks.
I calculate Person B's leave to be 24 days leave for the year.
That link from WindUp is for Irish holidays, so not sure it is of any use to you.
Karl Limpert
Employment Law Clinic