Unless you will arrive at a very odd hour, it will probably be easier and less expensive to get a plug adapter at your European destination than in the States. U.S airport prices tend to be high and the things are not widely available elsewhere on these shores.

U.S. phone cords work in continental Europe but not in the U.K. Phone jack adapters are easy to get there, though. In addition, business hotels often have RJ-11 ports in the rooms, and the concierge should have an adapter.