A level 3 course usually takes 2 yrs to complete (possibly longer depending on your circumstances), the OU shouldnt need to be told about the apprenticeship as its technically a job. As for the NVQ fees, if the nursery is partnered with a college to deliver the course then you shouldn't have to pay if they consider you a full time student, but if you are a part time student or are entering as a private candidate you may have to pay (or your work may pay for you.)
I honestly wouldnt bother doing the apprenticeship and the level 3 if you are doing a degree. It makes more sense to get a proper well paid job (even if its not in the childcare sector) to support you through your studies and then get experience working with children as a volunteer/hobby instead. Once you obtain your degree, no-one will care about the Level 3.
All the best.