The First Train Ride Ever

In Half Blood Prince, he and Ron take the Hogwarts Express back to London when they go home for Christmas. This is Harry's first exposure to the wizarding world. He doesn't even get on the train and he doesn't know why they have to fly a car. The one journey I think he ever had that was normal, was correct me if this is only a movie is him traveling by train in book four. So where is Grumold placed then? Anyway, that was my fun little, I miss London segment.