Fourplay (2001)

Allen, the British producer of a successful TV show, is married to beautiful Carly, the star of his show. Ben is a young American, hired to write the script for their show, falls in love and marries sexy French girl Fiona, a make up artist for the show. They all live in London and spend much of their time - both at work and in private - together and it isn't long before they each have an affair with the partner of the other.