I picked up the dark coloured carpet runner. This seems to make the hallway look very narrow. I suggest to perhaps try and remove it and see if it looks wider without it. My suggestion is yes it will. For the side wide cavity in the wall surface, you have a choice as others mentioned. However, do stay away from dark coloured paintings if necessary as it does make the hallway look narrower. My choice would be, remove the dark carpet from the hallway and use a large mirror in the wall area. It is than your choice what to put on the surface area of the cavity to compliment the mirror.

custom made vanity and wall cabinets should only be needed if you have awkward sizes as an off the shelf cabinet allows you to see and touch the product and is often much more economical than custom made ...unless you need to keep some special supplies (eg 24 pack of toilet rolls?) i suggest that a base cabinet need only be 450-500 deep which is plenty for folded towels and drawers and the in wall cabinet about 150mm deep (including most of the cabinet inside the wall and only a small frame for doors and mirrors projecting out) but the in wall cabinet may depend on existing wall studs and electrical wiring so think about what you would put inside the cabinets and only have enough inside cabinet space for those items (maximum toilet roll or fat shampoo bottle about 120mm...in small bathrooms the extra floor space makes drying and dresssing much more comfortable and by rotating the shower in the family bathroom there would be less wet floor in the walkway and if the vanity in the ensuite is away from the corner you can allow space for a handtowel and/or a very convenient space to hang a hair dryer ...

We too live in a cold winter climate with our bathrooms all on the southern side and faced similar issues as you do. One smaller bathroom does not have a window so we put in a Velux skylight which provides amazing natural light through the day. This may not be to your liking, especially if you have a period home. We also use heated towel rails and under tile heating (just enough to take the chill off and stop mould) in winter. Although we have a light in the shower recess, a bonus is the large fixed shower head with inbuilt LED, which at night gives the feeling of showering under moonlight. We chose light colours and mirrored recessed cabinets to reflect as much natural light as possible.

I would re-evaluate my brief, my budget and my site. It is another case of trying to squeeze too many rooms into too small a space and compromising the living space. If you draw furniture to scale in your living room then you will see that it is undersized for a four bedroom home. With the best orientation going to the garage door and bedroom 4 I would look at a complete redesign by pushing some of the bedrooms to the rear, and a central courtyard to give you an opportunity for north facing light to a living room. There is nothing nice about the current design and will feel like an apartment with little resale appeal. The designer has shown no flair or imagination in this "gun-barrel" floorplan, and is a variation on a concept that has been around for centuries. But your biggest problem is the number of rooms. Do you really need 4 bedrooms plus a study and 2.5 bathrooms, a long wasteful hallway, and only one modestly sized open plan living area and kitchen on a narrow block? I would start again with a smaller brief and a designer who can challenge your thinking about what good small house design actually means. Small house design is the hardest to do really well, so don't use a large house designer. Dr Retro of Dr Retro House Calls and Dr Retro Virtual Visits