Hello Dee, I would 'mirror image' your plan and have the kitchen against the original part of the house (to the left of your step down) and still with the island. You could then have sliding doors facing both decks, and hopefully a beautiful outlook to your garden, also a lovely vista when you walk down the steps... your living dining furniture will have the feel of more room against windows, rather than boxed in by walls.

I would paint your bookshelf the same colour as the walls and stuff it with, well, books! I would paint the built-in corner unit to match and just use it for potplants - ivy that hangs down would look good. As for the coffee table, if the room is small, what I did in our little family room was hunted around and found a large curved hunk of tempered glass from Freedom and it sort of 'floats' and looks invisible in some lights. Seriously, I think the line was called Ghost and was very reasonable (they also had a side table to match). Throw a bit of cherry red around and see how it looks with the creams and the taupes. Here is a pic of the coffee table.

Not sure on Heatcharm but will Google shortly. The conduit for wiring and the wiring itself for TV/etc is usually installed during construction (rough in electrical stage) before the plasterboard and stonework is installed. There's not usually any access once the heater is installed. Xbox, etc., not a silly question at all. Quite the opposite actually! In my experience it's usually not in this room or it's in some joinery. I'd do some more investigations at this stage maybe do some more Google searches, look at pictures on Houzz, etc. For me I'd add some timber joinery (shelves, drawers, etc.) to house wood for heater, Xbox, books, DVD's, etc. either side of the fireplace.

I mentioned earlier to think about dropping the wall next to the stairs to hip or slightly higher height to allow for the TV, as this would further open up the top floor and perhaps show the street art, ie the framed print. I know that you don't want anything else hanging from the ceiling but because of the ceiling height you will need a reverse hanging fan to bring all the warm air down into the room that will sit up there if you don't. The heater is because you had one shown in your posted floor plan, this is one of the fires available on my 1997 CAD program, that's the colour it comes in but can be changed within the program cheers