Under 18 Accommodation

Hello, I am an international student and will be under 18 on my arrival to UK uni in sep. I see that I need to fill in some kind of UK guardian consent form but I’m not really clear about it. If I don’t have any family members living in the UK, do I need to appoint a guardian from the AEGIS agent? And will I be staying in the guardian’s home, or are there under 18 accommodations in most unis? (Specifically UCL)

Thanks for any information!