Thanks for the info. I have been researching now for some months and have quite a lot of information. Visited all the online sites.
Re ships log, I was hoping that they were held in Portsmouth as that would be easier for me to visit. The details on the uboat.net site are not complete and a few errors.
I have quite a few copies of the Navy Lists but as far as I can see you need the captain's name first to check what vessels he commanded. I might be reading the list wrong.
Thanks again for all information, gratefully received.