Private room and bathroom from April - September / October

Hello!
I am looking for a private room with private bathroom between April - October (or September). I am originally Czech, but have lived in Canada for a long time and will be working this summer as a Cruise Director on River ships. I will therefore be "home" usually only 1 week each month, but I would like to have home-base instead of staying in hotels each time. Ideally I am looking for a central location: Mitte, Kreuzberg, Friedrichshain, Prenzlauer Berg (Pankow), Charlottenburg-Wilmersdorf. I am very social, but because of the nature of my work (dealing with hundreds of people sometimes 28 days straight), I need some peace and quiet and “alone time”. I am 43, but fit in very well with any age group (most of my friends are younger, but I also work with older clientele). I'm a passionate about travel and enjoy the arts and culture. I will be in London until mid April, but can discuss via Skype.
Many thanks!
Patricia