I've found Naval History.net really useful for RN stuff - through I guess you're maybe just looking for the German side of things at this point?
Potentially useful:
Various RN Home Commands and Fleets OOB
RN Ships damaged or sunk by enemy action 1939-1945
RN Minelaying operations - because I'm sure you want the Germans to have the best possible invasion routes. Best for us.
Admiralty War Diaries - what looks like a ton of very granular detail.
Battle of Britain - with monthly loss stats
Maps - mostly from British perspective, and sadly nothing for hypothetical campaigns.
I'll be doing research on the Kaiserlichemarine at some point, and as with British sources I imagine there's a an order of magnitude more info out there for WWII than for 1890, so I'll shout you if I come across anything relevant.