So far as I'm aware the Royal Marines Commandos have been deployed operationally in areas of conflict every year from 1942, except 1969.
In 1998 there was still conflict in Kosovo, Former Yugoslavia, in Northern Iraq with the Kurds facing persecution and the Northern Ireland peace accord, whilst signed on Good Friday in 1998, certainly did not initially see a complete nor immediate cessation of hostilities. Also in 1998 part of 40 Commando deployed to the Congo to facilitate the safe evacuation of UK ex-patriots from Kinshasa City.