I have a brilliant child minder with similar fee stuff:
holidays as and when but she always gives me a months notice, and doesnt charge
full fees for absent, sick child and our hols
she doesnt charge for when she is of sick, but she hasnt had a day off in the three years i have known her.
half an hour late thing i dont know.
I think you'll find that even though it seems steep you will hardly notice the extras.
I took mine out of nursery as they were not giving good enough care and had some very disturbing problems with them, i found nurseries too commercial, but each to their own :-)
I would look into a back up plan tho just in case.