This may be too late for your researches given the date of your posts on this subject but the National Archive at Kew holds file ADM 137/3897 which contains comprehensive information, apparently freely given by Steuermann Bernhard Haack who had served on UC-31 prior to his capture. The file details his career from merchant navy to U-76, UB-35 and UC-32 to UC-31. He seems to have been a remarkable character who later succeeded in escaping from Stobs POW Camp in the Scottish border only to be recaptured with other U-boat prisoners in a boat off Cresswell in Northumberland.

The same file also contains information on Obersteuermann Wilhelm Skau who was one of the survivors of UC-32 sunk off Sunderland in 1917. His career path was somewhat different to that of Haack as he was lifted direct from the reserve.