Pavel,
I'm not the right person to be giving you any advice about the gay lifestyle or coming out, etc. I can say that, without respect to the reasons, friendships are fragile things. While they are easily made for some people and more difficult for others, they are easily lost for all of us. You are moving 1,000 miles away from home and from these friends you are concerned about. That distance will put a strain on a friendship. I would guess distance is the reason you are moving 1,000 miles. You don't want that kind of strain on your most important friendship.
You should try to maintain those old friendships...and it's a lot easier to do these days than it was when I moved from home. If those friendships don't survive for whatever reason, don't dwell on the reason. If they can't help you make the move to London, just think about how great a distance 1,000 miles is. You are asking a lot. Stay in touch with them; visit them when you are back home. Give them every opportunity to remain your friend.
Most important, think of all the new friends you are going to make. Your very best friend will be there with you. I doubt you will ever be lacking for friends.
Have a safe trip.