Current status (as of last night).
Starting to mark out speaker & spotlight locations, need to move a few pipes / air conditioning tubes around before the isolation / plasterboard goes on, but generally looking good.
You can see a cut out in the floor (which managed to miss the underfloor heating) which will be the line to carry power to the electric seats. That is 440cm back from the far wall, which will be 4m back from the screen - which is my MLP. You can see the stone flooring starts at 623cm back.
Speakers and spotlights will be installed in niches built using the sound proof plasterboard, isolation & sound proofing layer so that we don't have to cut any holes in it once it's finished.
Will keep the updates coming...