For a lightweight package of 4 DVDs probably the air mail service provided by Royal Mail. When I've posted stuff to the US that's the route I take.I wonder what mailing company they will use to deliver in the U.S.?
Just a laugh .... The Royal Mail sticker is quite an impressive thing in "gold" leaf showing HRHs head. One of my correspondents in the States was taken aback when his little girl rushed in from taking the post with "Daddy, Daddy, you've got a letter from the Queen of England!!"