I was Chief Engineer on Lakespan Ontario in winter of 1982 when we picked her up from layup in Montreal, shipped a cargo of package timber in Gros Coccuna (?), Quebec for Warren Point, Northern Ireland before bringing her to Glasgow (Yorkhill Quay) for layup. Soon after, the MOD decided to bareboat charter her and she had many modifications done (some much to the amusement of more "commercial" merchant seamen !) and changed to RFA / British flag / Lloyds Class in Stephens Basin. Good little job.
Sir Caradoc was as you correctly state formerly the Grey Master chartered as an interim replacement for Sir Galahad the Falklands casualty. She was operated mainly on the Marchwood to Antwerp BAOR maintenence run but did occasionally go further afield.
When the new Sir Galahad came into service she was Caradoc was actually purchased by the MOD and sold on to Norwegian owners who converted her into a RO-RO ferry with limited passenger facilities, this would have been in 1988. I have some pictures of her after her conversion which I will post soon. I do not know if she is still operating.
In RFA Service she was affectionately known as Sir Carrycot as she was often the first appointment for "Baby Captain".