Hi Jones.... i will be sailing to Norway in July 09, what was the cruise like etc.
On a 1 week cruise there will probably be at least one formal night. When you get your tickets it will tell you exactly how many formal nights there are.
Generally a suit or dinner jacket is suggested for men and cocktail dreses for woman. To be honest though, I've worn a jacket, tie and a pair of slacks in the past.
Fred Olsen cruises often also include a red, white and blue (British Night) and a country western theme night. However, you don't have dress in a union flag or like John Wayne. Casual clothing is fine.
2 formal nights - one welcome captains cocktail party and the 2nd is the farewell cruise. Other than that you can dress smart and the first and last night casual. However for men. they must wear either a shirt and tie or a jacket with a shirt without a tie for the nights which are not formal and not casual - those inbetween.