I sent the information to Roy; lo and behold he was able to find the following on the website findmypast.co.uk:
Name of Ship: Carnarvon Castle
Date of Departure: 22/7/47
Port of Departure: Southampton
Port at which passengers have contracted to land: Capetown
Name of Passenger: I. Davies
Last Address: 318 Longton Road, Stoke on Trent
Country of intended permanent residence: S.Rhodesia
Occupation: Mech Ex
Roy had been looking for my grandfathers information before but he had never known the exact date or the name of the ship. Thanks to Uncle Glyn we were able to discover this. I was also able to let Roy know he traveled alone since the rest of the family departed at a later date so Idris could set up home for them.
The "Castle" line of ships were all former war ships in the British Navy which were decommissioned and became cruise ships after WW2. The last known address mentioned here is the home of Harold and Anne Griffiths where my Great Aunt Ruth lived until she was married. Idris moved his family in with them during the months of his departure.
As for Idris occupation. This is still somewhat of a mystery. We think he wrote "Mech Ex" though it may have been "Mech En". This might stand for Mechanical Engineer or perhaps Mechanical Experience? We're not too sure. He definitely did not have a degree although he was quite mechanical minded. In some of the interview notes with my Aunt Wendy she mentioned that at some point she believed Idris to have worked mechanically on airplanes during WW2. We also know he was a munitions inspector.
When he arrived in Southern Rhodesia, Wendy is sure that he worked on farm machines for a while, perhaps he put this down as his occupation because mechanical skills were something he felt confident with.
Iris, Wendy and Glyn all traveled on the Warwick Castle. The relevant pages that have been scanned onto the findmypast.co.uk site are all black and obviously were not scanned correctly. Roy has requested for this information to be updated but it may take several months.
In the mean time I now have this information to add to the story of "The Grandfather I Never Knew."