School preschools tend to be shorter hours and term time only, they set them up for school. It's usually a load cheaper so if you're tied to school already it works out better.
Just because your child is at a school nursery does not mean they are guaranteed a place at a school- it’s done by a number of factors; where you live, if they have a sibling at the school etc. but you don’t get priority for using the pre school. I have chosen to send my children to the pre school attached to the primary school I’d like them to go to but that’s mainly because I can use all 30 funded hours without paying any top up fees and the pre school has been rated outstanding by ofsted. They also run before school and after school clubs so my kids can go 8.15-5.30pm if needed
I think pre schools attached to a school are term time and they're usually shorter hours than a nursery (like school) so maybe until 3pm ish? X