Want to change my university how do i do this?

I have applied for university already (last year) and got an interview at Brighton university, I passed the university and got a place there for studying film studies in 2017 as I took a year out.

However, whilst having a lot of time to think about university as i'm currently in my gap year i've decided i want to change university and go to study Film in a university in London as i'd like to study there.

How would I do this? I've got all of my grades from leaving college I just have no idea of how I change university.

Do I have to apply through ucas again? Do I just have to delete my account? Or do I have to apply through the university somehow?
Can I still use my same personal statement?

Thankyou for helping, i'm just in a pickle right now and don't really know how to sort this situation out at all.