Michelle, I have just decided to start keeping a list of real known internees, like yours. I'm going to make a Word file for myself, and I will keep the info that you have posted. If you would like to PM me contact info for yourself, then maybe one of these days when I get around to trying to assemble this, I might get in touch. Maybe eventually the story can be told from the real life experiences of relatives like yours and mine. It just seems to me that that story has not yet been told from that perspective, and that it's important. There were almost 30,000 of them, so there ought to be quite a few stories out there somewhere, but hard to find, no doubt.
You are really really lucky to have found so much information for this person. I still have nothing really on mine except that I know he was interned. I did try the source you mention some time ago, but there was nothing there for my man, and, as far as I know, my ggrandmother never bothered to get herself renaturalized; nothing at Kew, alas.
I did know that many of the internees who died and were buried at St. Patricks were eventually moved to Cannock Chase. One can find out about the ones that are there by contacting the Commonwealth War Graves Commission - they do not list these people on their site, but they do have some information and will respond to email inquiries. Nothing for my man there either!
I will certainly let you know if I run into Johann. If you know where he had come from, where he lived and what he did for a living, I will put that in my list as well, for starters. Maybe one day this will turn into a book.