Welcome to our forum.
I like your intro, it explains a lot and it sounds like you have had a good poly relationship so far.
Correct me if I am wrong, but it sounds like there is some tension between you and the other woman, largely because of sharing a domicile together and the two of you just have different styles of housekeeping and that. So, you are thinking about moving out and getting your own flat, but you'll still continue in your romantic involvement with the guy, and continue as friends with the other lady? Correct me on any points I'm mistaken on.
Right now, it sounds like you have a V relationship: He is romantically involved with each of you ladies, but the ladies are just friends. That makes him the "hinge of the V," and the ladies the "arms of the V." It sounds like you previously had a triad; that is, all three of you were romantically involved with each other. V's and triads are probably the two most common "shapes of poly families," but there are many others (quads, Z's, etc.). I would actually call a three-armed V a "Y."
I hope you will enjoy our site, and learn a lot on our various threads. Post if you have any thoughts or questions you want to share.