I found quite a bit of information about the MV/HMS Princess Victoria, including personal accounts from other descendants of crew members, on wrecksite.eu - a fantastic source of information about historic wrecks.
Princess Victoria was built in 1939 as the first stern loading car ferry for the London Midland & Scottish Railway Co. and was used on the Stranraer to Larne route. Engines by Wm Denny & Sulzer diesels, 21 knots (Sulzer constructed the port engine in Winterthur, whilst Denny constructed the starboard in Dumbarton). She was taken over by the Admiralty as an auxiliary minelayer. On the 19th May 1940 she struck a mine off the entrance to the Humber and sank quickly. Captain J.B.E. Hall, three officers and 32 ratings were killed. See HMS Princess Victoria on wrecksite.eu for further information.