It varies depending on the university and what accommodation you are applying for. For example, some may require a deposit whereas others may not. I'd highly recommend going to view multiple accommodations if you'd like to stay in university owned, as they may ask you to rank your choices in order of preference. If you can see these in person (e.g. at an open day) then that would be ideal but if not, take a good look online and ask the accommodation team if you have any questions.
Private student accommodation is also worth considering. For example, at Student Roost many of our accommodations come with additional facilities included in the bills (plus a packed events calendar) so it ends up being good value for money.
Hope this helps!