The sofas are quite a strong look for the small space. Can you replace these? Also one sofa and one/two armchairs might be better. The red touches are quite bright too. Use pops of colour in things like cushions then you can change the colours seasonally.

Unless you want to put the tv over the fireplace, I would suggest a bespoke unit under the stairs to house the tv and also any ornaments to make it a feature. Pics attached just showing ideas. This could be dear unless you're good at diy so another option is to get a low unit to fit the space and add white shelves over the top to look as if they fit the space. I would consider moving the table and light by the window and centralising the sofa under the window. Maybe also add a coffee table or trunk to bring furniture into the middle of the room. In terms of decor what is your preferred style for people to help with paint and wallpaper? Are you keep all the existing furniture and curtains so does it need to tie in with the red?

If the room is small I'd avoid warm colours on the walls. A Contemporary style always looks good with victorian features or something that is elegant and classical but still contemporary maybe in pale greys. A statement light or chandelier would also look great. Mirrors can work wonders in small rooms and also help bounce light like the wall to ŵall mirror SJD pictured or mirrors or mirror tiles in the chimney recess like this one pictured from AO.com. They aren't cheap ( personally love antiqued ones which are definitely not cheap!) though. A glass coffee table would help if not though so you can still see the floor space. Do you have pics? What light does the room get? Are you keeping all existing furniture and flooring etc?

Looks like a lovely place. I don't see much wrong with it. The sofa is a little stark looking but I’m sure if you get some scatter cushions this would soften the white. Others here are better with that sort of advice but if you can coordinate them with your textile wall hanging I think it will do the trick. The art on the walls looks good but I would align the painting over the TV differently and lower the clock by about 50 cm.