Bank holidays have no special place in employment law. All that the law says is that the total number of days (paid) holiday you should have must not be lower than 4 x 5.6 = 22.4. It's completely irrelevant as to when you receive those days off.
However the law does require that part-time employees are treated in the same way as full-time staff with regard to holidays. Whether that requirement actually benefits you would depend upon whether bank holiday leave (for full-time employees) is within their statutory holiday allowance or additional to it.
For example, if the full time employees get 5 x 5.6 = 28 days paid holiday per year (INCLUDING bank holidays) and you get 4 x 5.6 days, then you're being treated in exactly the same way. But if the full-time employees get 28 days paid holiday PLUS 8 paid bank holidays, then you should get 22.4 days paid holiday PLUS an allowance equivalent to 0.8 x 8 days = 6.4 days holiday.