Bit of a long shot. I reads it in the early 90s so it's quite old.
It's about a girl who moves to London. Can't even remember if she moves with her family or not. I think she has a brother.
I just remember that she is looking out of her window and there are trees lining the street, she must have moved from the countryside.
Think there was an attic room, she eventually settles and makes a friend.