Yes light and reflective surfaces, mirrors etc will improve the light levels. So The black rug is not a good idea, move it to another room! The idea of half shutters sounds good, though obviously these should be light coloured / white, don't go for darker timber slats. Which colours do you like? It's a good idea to collect a pile of interiors magazines and colour copy the colour schemes you like, get some match pots, but remember to always choose a lighter shade of the colour you like. This is because over a larger area paint colours appear stronger, so a couple of shades lighter will usually give you the effect you want. You could mix wall colours for example have two larger walls white or off white and the others a colour, perhaps lighter blue green, soft light green, soft amethyst purple/grey. When I start a colour scheme I sometimes start with a coloured patterened fabric I'm using for curtains or cushions and pick up the lighter tones on the walls and sofa upholstery for example.

An image of your space would really help us advice you. The Myers Touch team

At the moment the kitchen walls are F&B New White which is ok but not suitable for the adjacent rooms as it is too yellow looking as I need to take the oatmeal sofa in the living room into consideration. The three rooms lead into each other and are open plan to each other. The living room is the darkest and the others have good light. Kitchen is to the left of dining room and living room is behind dining room. The house is cottage style but no beams

I am north facing and also in the north. Maybe our light is different here, but I have a similar (smaller) extension with one velux and it is full of light. What it doesn’t get is direct sunlight, except early on summer mornings. I also had to block up half of a floor to ceiling window in a north facing bedroom and the loss of light is minimal.