When you start, you will get your timetable which will show when you're on theory and when you're on placement.
The timetable will show lecture/seminar times for when you're in uni on theory blocks. These lectures and seminars will be scheduled by the university, the timetable is fixed by them.
As for placement... you can ask for certain shifts but this cannot be guaranteed and is 100% manager discretion. All student nurses have to do 2300 over the 3 years (20-21 weeks a year at 37.5 hours a week), including all shifts. If a placement is 9-5 Monday-Friday (community, outpatients, clinics), then you need to so these hours in order to complete placement hours. If a placement does shifts (hospital wards, nursing homes), these can be shifts such as 730am-830pm days/8pm-8am nights, or days split into early/late shifts. "I can't start til 8am because of childcare" doesn't wash with a shift that starts 7-730am.