I think it's complex, but for those saying 'don't you get paid bank holidays'... well, yes and no... I'm paid a monthly salary, so I don't get less for the months which include a bank holiday, but my salary includes 24 days paid leave plus bank holidays. Argue it either way as to whether I am paid for those, or they've been taken into account.
DS is in full time nursery, and we pay the same each month, even though they close for a week at Christmas and aren't open bank holidays.
BUT if my DC was only in, for example, Mondays and Tuesdays, then I think it's reasonable to feel it's unfair as I would be disproportionately hit by the bank holidays. Not sure what the answer is though.