with David Jessel , Sue Cook and film reporter Ed Boyle This week: half a million couples in Britain are living together outside marriage. But as bedlock without wedlock means losing the law's protection, many couples are now following the American example of 'cohabitation contracts' to regulate everything from dividing up the joint home to sharing the washing-up. Are these contracts legal? Studio director PIETER MORPURGO Producer ALAN BOOKBINDER