In case anyone is interested I found the Cunard dress code...
Formal evening wear consists of an evening or cocktail dress or smart trouser suit for ladies, a tuxedo, dinner jacket or dark suit for men. Military or Award decorations may be worn on formal nights. A range of gentleman's formal wear is available to hire on board.
Semi formal evenings would consist of an elegant dress, or smart trouser suit outfit for ladies, a smart shirt with tie and trousers with a blazer or sports jacket for men.
Elegant Casual nights require clothing such as stylish resort or leisure wear. Casual dresses or smart separates for ladies, open neck polo shirts and casual trousers (no jeans or shorts) for men. Jacket required but no tie. Children under 18 do not have a dress code but should dress as smart as possible in relation to the above