As an international student living far away from the uk, I initially found it very hard to find accomodation, this was primarily due to the fact that i had left it was too late, and had missed alot of the required dates. Thankfully though accomodation for students.com was very helpful with regards to me finding a place to stay.
As An international student I stongly advise that you start looking for a place to stay quite early in the year as soon as you know where you are going to go. And although you might have a friend coming to the uk with you I stronggly suggest that you dont house mate.
This is not advisable because even though you are almost garunteed to get along fine, neither of you will really get to know the ins and outs of where you are staying and also make it harder to meet new people. Because of this I strongly suggest halls of residence for you first year, and if that is not possible, find a house mate from the uk.
Another tip to remember would be the more the merrier. When you are looking for accomodation and its your first year you want to be around lots of people so you have a wider variety of people who you can meet and interact with, and then meet their friends etc. I think its important that you use you accomodation situation to meet people in you early days as a student in a new place.
I hope I have been helpful.