If you reply telling us how many hours per week a full-timer works and how many days holiday a full-timer gets, one of us will work it out for you. Also tell us whether full-timers get 8 public holidays per year, and which days of the week your work (if fixed). Yes this has an impact, because you cannot automatically assume you can expect all the Monday bank holidays, if you normally work a Monday.
Employers have an amazing ability to get this calculation wrong in situations where a part-timer works different days in a week.
The only way we will be able to work this out is in holiday hours per year, and each shift you take as holiday will deduct 4 hours of holiday.