En suite shower refurbishment and fitting in Mayfair, London

Looks alright, but it's more a 'DURING & AFTER'.

Hello Claire, not sure why no one has answered this. How much do you want to spend is the main question? I would open out across the back of the house incorporating some of the grey room and hall. That would give Kitchen dining living with a snug living space at the front. Add some bifold or cheaper sliding doors across the back in the dining living section. If doors are glass into this area from the hall, that can be a nice feature to be able to see right through as you enter the house. The downstairs loo can go underneath the stairs as drainage looks to be on that side. Alternatively, turn around the bottom of the stairs as winders and fit the loo in next to the porch. The en-suite at first floor could be a narrow strip in between the two large bedrooms. or sacrifice one of the smaller bedrooms.

Thanks for all your replies - I really appreciate it. We do currently need all four bedrooms as we have 3 children. Whether it is our forever home really depends on how much we can expand. It is a semi detached 1930s property. The current owners have already extended to the side to create a fourth bedroom downstairs and have extended to the rear for a bigger kitchen. We are hoping to eventually extend on top of the current side extension - I'm guessing if we did that we could make bedroom four bigger and build in to it to create the en-suite? Here is the whole floor plan