Hi I suggest as a starting point searching the photos on Houzz for say, contemporary basement' then look at the info. It will give you the architects or builders who designed/created,, Obviously not as good as a recommendation, but a start.

Hi. I think any dark, rich colour could work well (would paint the skirts in the wall colour) but if you didn't want to paint the furniture either a really deep teal or inky blue would work well. Perhaps use ochre or burnt orange as accent colours or moss or emerald/grass green work really well with an inky blue. I assume the ceilings aren't tanked so you'll need a ceiling fix pole? Having floor to ceiling curtains will make it feel taller. I'd also have a tall portrait leaner mirror on the wall opposite the window to make it feel taller and to bounce light (do you know where the stud work is for attaching things to walls?) Could you have a light weight canvas hung on the chimney breast attached with those sticky pads? Agree re lighting and would also add 1/2 floor lamps. Is an electric stove in budget for the chimney? My only reservation is dark walls against a white ceiling. I think my basement is the same height and I deliberated for ages and in the end painted it all white :) there is an argument that dark ceilings can create depth as you can't see where they end.. also an argument re white gloss or Matt finish for the ceilings! If you did go for dark walls though i might consider a mid shade for the ceiling

I’ve just had the same issue and I opted to get all walls plastered then sanded down to give completely smooth walls. They were then painted and the finish was excellent. I paid for tradesmen to do all of this as I wouldn’t have achieved such a quality finish.

In my opinion it depends on budget. The best option is to take off the wood cladding and coving and then get a plasterer in. The budget option is to sugar soap these walls to ensure there is no wallpaper paste residue, then fill and sand any cracks and also use decorators calk to fill cracks in corners and next to woodwork. Then you need to mist coat the walls which is basically a watered down coat of paint. When that is dry it will need two rollered coats of emulsion (3 if it’s a strong colour). A very flat Matt paint shows imperfections least. After the first coat of paint check it for any bits that might need more filling. In conclusion the key to a nice finish on the walls is lots of preparation and then a low/ no sheen paint.