Open days are busy, so go with a short list of questions (sample advice from our admissions team).
Ask to see the course map for your subject: which modules are compulsory, which are optional and how big the final project is. Ask how many hours of teaching a week Year 1 has, and how big the seminar groups are.
Then ask current students where they lived in first year, and what they wish they had known. Book your place from the open days page.