I don't mind the current colours although a greys and beiges tend to suck light out of a room, a brighter colour rather than just white will help. I agree with much of what Jill says above, with a few tweaks ... the lighting needs attention. The room needs some interest, colour and texture to create depth. Get a larger rug, more colourful, with organic pattern which draws the eye outward. Big enough to sit the furniture on. Pick up some of the colours from the new rug and get some cushions. A couple of plants would help with texture and add life to the room. I know you are using the mirrors to add light and space but the one under the stairs is just reflecting the underneath of the stairs ... try a colourful print of a pathway between trees for example, to draw the eye beyond the room otherwise it's a bit bland. The TV is just on a stand that is too small and a bit low, go for a wider piece or try positioning the unit against the other wall in that same corner so it is facing the sofas, then the TV won't look so out of balance. If you make the room a bit livelier and interesting the light issue won't be such a problem. Consider pale turquoise walls for example rather than just white and add some artwork.

I really like your herringbone tiles, am considering something similar so looking forward to more of your photos. I would go with painted behind the wall hung toilet as think it may get overwhelming with more tile. Where are your wall tiles from - they are a good combination of width and length?

You will need planning approval for a dormer on the front of the house. It is worth calling your local planning department and asking whether they might be minded to approve such an addition to a house in your area - afraid planning departments often wont approve dormers to the front of a house. If you are in the conservation area you will probably need planning permission for any works to the house. If your house is not listed and not in the conservation area it is worth investigating maximising the space you can add to the rear under permitted development - details can be found on the planning portal https://ecab.planningportal.co.uk/uploads/miniguides/lofts/Lofts.pdf when setting out to do any work under permitted development, for piece of mind apply to the planning department for a Lawful Development Certificate - this is not the same as planning permission but is proof that you house extension/dormer is lawful

Hi Barnaby, Sounds like a great buy and a fab family home! Having been through a very similar situation in the last 6 months (moving into a house where the back wall had been extended and the house was left with a very similar 'steel and nibs' to your kitchen, where it had been opened up) I'd definitely recommend getting some advice from a few different people. Two builders told us it would be impossible to get rid of the visible RSJs and the nibs of the old external wall. It was only when I persevered and asked an architect to come and have a look and got a structural engineer in that we realised it was completely possible and far less expensive than we thought. We only ended up spending £2,000 on fees (£500 architect and £1500 structural engineer) and £12,000 on building works and it has completely transformed the space. If you're lucky enough to find a creative builder they could be really helpful with the layout but my experience was that they are more about the 'doing' and 'practicalities'. I found getting some independent design advice (from a concept planner) on the space and layout super helpful and then once we had an idea of what we wanted we were able to ask a couple of builders to price up. The designing of the layout was a fraction of the cost of anything else and saved us a lot of money in the long run. You might want to have a think about chatting to a concept planner (there are several great ones on here) and get an idea of some designs and costs. Just a suggestion :)