Sponsors Question

Hi.

I am coming to the UK in the summer to study a college course for two years and I am looking for some information to do with having a sponsor. My questions are:

1: Does my sponsor have to be someone living in the UK already or can it be family here in the USA who are going to help fund me during my studies?

2: Is it posssible to have more than one sponsor like one from the UK and one from the USA?

3. What additional information should my sponsor(s) send with my application

And an additional question, not on the topic exactly but i just thought of it,

If I apply to the New York office for my Visa, will I have to go there for an interview or will I get interviewed as I enter the UK as a student

Thanks for any help or advice, any would be appreciated