Thank you so much for all this positive feedback!
I’m sorry for a late reply but here are all the details about the scene. If you need to know anything else please ask ahead.
I used 4.10.2 version of the engine. I tried 4.11 with portals but something went wrong, so I decided to stick to stable release.
Lightmass and Rendering:
In *BaseLightmass.ini *I changed just one setting:
NumHemisphereSamples=256
And the World Settings for Lightmass
For lighting I used only Skylight with a HDRI attached to it (one form Peter Guthrie collection)
Rendering of the Lightmass too 2.5 hours but I also tweaked some settings in Swarm Agent:
I changed Processor Count to my maximum available and Priority to normal. This helped to squeeze maximum juice from my machine, but I have to warn you if you pump up those settings your entire resources will be used up and you can barely move mouse cursor while Lightmass is being rendered.
For walls and floors I used mostly 512 and 1024 size of textures and that seems to be enough, however my walls are broken down into smaller chunks
Reflections:
I followed this article to boost SSR in the scene http://http://oliverm-h.blogspot.co.uk/2014/08/ue4-improving-ssr.html it was very helpful and I managed to get the effect I wanted.
In my main PostProcessVolume I have those settings for Screen Space Reflections:
Intensity = 100
Quality = 100
Max Roughness = 1.0
Rest of the reflections is done by Captures. Here’s the setup:
Primary Captures
Secondary Captures
And the final touch - AA 
I really went to town with the settings on AA and it really made the difference. In the end I was not aiming for performance but photo-realism and in the end I was exporting frames from Matinee so frame rate was not an issue here.
Hope you will find this breakdown helpful and if you have any other questions just ask!
