However you hang it, keep in mind that once the sheer fabric falls in front of the back fabric, the sheer will change color. So, let’s say you have pulled back the thermals, but not the sheers. Where the sheers hang over the stacked back thermals will not be the same color as the rest of the window. It doesn’t sound like a big deal until you see it. It is very obvious.

I would avoid using dark colors in a room with wood paneling as it would make your space gloomy. You also don't need to match the dining room set. I would go with a very light and fresh cream with very light brown stripes. You could also choose something like this (https://s-media-cache-ak0.pinimg.com/236x/57/8f/6a/578f6abfb4e7b991e594b64cf4f2c174.jpg) to add the blue to the mix and have more colors.

Yes, the brown wall is actually deep purple (aubergine). The carpet is more dark grey than brown. It is not a commercial place, but a large family home, and all the extra chairs are around because we were about to have 22 in for dinner, so the table was fully extended to it's 6metres! (The lounge is totally separate to this room, this is family space, so has the old sofas for sacking out on) But I really appreciate all suggestions and comments as it would be good to pull it together, even when entertaining so many. Cheers!

You are correct the place does and always will look a bit sparse when you only have blinds. The question with curtains is sometimes dependant on what climate you live in and I am not sure where you are so I am going to say. If you need curtains for heat go for a quality curtain to the floor with a fabric that is not stiff (as I discovered I now own after buying curtains off line for my spare rooms). The expensive curtains I brought for my living room have a softer texture and hang so much nicer. As I need Curtains / Roman blinds for heat I have backing fabric etc on the expensive made to measure ones, where as the cheaper ones are just thermals. If you only want to add a curtain for looks and do not require it for heat I would recommend going with a lovely sheer / half see through fabric that drapes really well, this will add a point of interest and you can colour match or add a loved colour to a bare - white on white - cream on cream - colour scheme.