Hi Samantha I know you said about not mounting the tv on the fireplace wall but there's actually some pretty clever stuff you can do with this and make sure it doesn't take away from the stone/whatever finish it is. It's definitely the most natural place to put it as blocking off one side of the fireplace will create imbalance and just won't be as practical to be honest. See below for some inspo... Hope this helps!

The installation looks like a robotic smilie face...

That’s a good shout actually. The bathroom would go along the side of bedroom 2 as well. Could have a wet room style shower in that thin bit.

I think breaking it in separate zones would help style it. But place the couch in the centre, coffee table in centre of the room with a 2 seater to the left and a L couch to the right. I would place the furniture on a big rug that would feed into the 'zone'. So imagine if TV is on the middle wall on the back, you can chill on the L couch comfortably and when people visit it's more social.  Then use smaller zones in the corners of the room, so the right of the room a single chair and side table as a little areal and perhaps bookshelves etc to the left of the room