I notice that you say "required"? This sounds like it is going to be a bit of a trial for you? To many people the "Formal" nights are a time to let yourself go and dress to impress! Men wearing dinner jackets and dress shirts, and women wearing ball gowns! That is one of the main attractions of a cruise for me and my partner. All that is "required" is a Jacket and tie for men, and a smart dress or trouser suit for women. The choice is yours! Happy cruising.
Extract from P&O website. "This is the opportunity for ladies to wear formal evening wear such as a ball gown, trouser suit or a cocktail dress. For men, a dinner jacket or tuxedo are the norm, otherwise a dark suit and tie or a kilt and jacket is fine."
We have just returned from a one week's cruise to the Fjords with P&O and the scenery was magnificent.
On a formal night the norm is men in Dinner Jackets, dress shirt etc. and the women in long dresses or floaty trousers with glitzy tops. I would say on our cruise well over 90% of men were wearing Dinner Suits with the remainder in Lounge suits. Hope this helps.