"Shake 'em off ... shake 'em off ..."
-- Uncle Vernon, upon making a sharp turn (PS3)
When thirty or forty letters come pouring out of the kitchen chimney at number four, Privet Drive, Uncle Vernon has had enough. He packs everyone into the car and drives around for hours. The family ends up in Cokeworth and stay the night in the Railview Hotel.
In the film, the letters come out of the living room fireplace, but in the books they are sitting in the kitchen:
On Sunday morning, Uncle Vernon sat down at the breakfast table looking tired and rather ill, but happy.
"No post on Sundays," he reminded them cheerfully as he spread marmalade on his newspapers, "no damn letters today --"
Something came whizzing down the kitchen chimney as he spoke and caught him sharply on the back of the head. Next moment, thirty or forty letters came pelting out of the fireplace like bullets. The Dursleys ducked, but Harry leapt into the air trying to catch one.
Uncle Vernon seized Harry around the waist and threw him into the hall. When Aunt Petunia and Dudley had run out with their arms over their faces, Uncle Vernon slammed the door shut. They could hear the letters still streaming into the room, bouncing off the walls and floor.
"That does it," said Uncle Vernon, trying to speak calmly but pulling great tufts out of his mustache at the same time. I want you all back here in five minutes ready to leave. We're going away. Just pack some clothes. No arguments!"