A well-made modular lounge earns its keep when you can reconfigure   modular sofa   pieces to suit the way you actually live. One weekend it needs to hold a crowd, the next it should face the telly comfortably, and sometimes it must convert into a sensible sleeping spot for visitors. The trick is to treat your sofa like a set of usable components, not a fixed object, and to plan the room around movement and sightlines rather than habit. Start with a quick reset: safety, floor