The per week factor to use for paid holidays is 5.6, so if you work 5 days a week (5x 5.6 = 28 days) if you work 6 days a week your statutory holiday entitlement is still 28 days, though in practice many companies give more than the minimum regardless of the days worked, if you work 2 days per week 11.2 days (2 x 5.6 = 11.2 days). Your holiday entitlement is for this number of days, which can include the statutory public holidays per year, but rarely do. Many employers now give pro-rata public holiday entitlement in an effort to be fair to part time workers.
The important thing to remember is that part time workers must be treated no less favourably than full time workers.