I found it. It’s easiest thing in the world - you actually have UPlanarReflectionComponent which you can include in place of your reflecting surface. You need only to rotate it properly to actually get PlanarReflection parallel (and in place) to reflecting surface. As I wrote before, multiple reflections are probably impossible on this stage of Unreal Engine (…shame), but other than that everything works great. Maybe reflection has too small resolution, but you can probably change it in UPlanarReflectionComponent properties.