"Rangatira" was not an ideal accommodation ship, as her cabins were designed for overnight use rather than long-term residence. However, modifications for her new function were limited to alteration of her cafeteria. Then she left Falmouth on 12 March, reaching Loch Kishorn on 14 March. "Rangatira" was in use in Loch Kishorn until May 1978. She visited Glasgow to be surveyed in October–November 1977 and again on 25 May 1978, when her charter to Sea Truck came to an end. On 18 March 1978 in Loch Kishorn the coastal tanker collided with her, causing minor damage. "Rangatira" was then repaired and altered for a four-year charter as an accommodation ship for the building of the Sullom Voe Terminal in the Shetland Islands. For this charter she was more thoroughly adapted. All her cabins were converted to single berths, a gymnasium and indoor games facilities for snooker and table tennis were installed and television lounges were built on her upper car deck. "Rangatira" reached Sullom Voe on 2 October. On 9 May 1981, Queen Elizabeth II officially opened Sullom Voe terminal, and afterwards dined aboard "Rangatira". The ship then returned to Falmouth to be laid up again, arriving on 5 July. The Union Company again sought a client to charter "Rangatira". Negotiations for her to be an accommodation ship for Pemex, Mexico's state-owned oil company, fell through. Then Blue Star Line entered negotiations for "Rangatira" to become a cruise ship off the coast of Africa, under the management of the Curnow Shipping Company which at the time ran that served Saint Helena and Ascension Island. This would have involved replacing her steam turbines with diesel engines and a complete refit of her accommodation. On 2 April 1982 Argentina invaded the Falkland Islands, and between 7 April and 12 May elements of a UK Task Force left Britain for a counter-invasion of the islands. "Rangatira" underwent sea trials for the UK Ministry of Defence, which on 15 May 1982 chartered her for possible service as a hospital ship. This was later changed to service as a barracks ship. "Rangatira" went to HM Naval Base Devonport, England where she was modified for war service. This included fitting underway replenishment equipment for bunkering at sea, adding a helicopter deck to her A-deck strong enough for a Boeing CH-47 Chinook, and arming with four Oerlikon 20 mm cannon on her upper decks.