If you want to sell quickly and at highest price possible, personally I would approach this from the angle of (a) minimise the weaknesses and (b) identity maybe 5 or 6 areas to introduce “wow” moments. When you’re wanting someone to fall in love and pay the higher price, you need to help create that moment.
-get PP for a fully extended modern kitchen but don’t build it. However do upgrade current kitchen with new colour, some new artwork (big) and some new lighting. Replace the countertops with something that looks expensive, likewise the handles. Style it maline with a bit of le creuset and some luxurious bits like e.g. a gorgeous kettle? It’s not going to be a super glam kitchen without a major spend, I think you should pump up the heart and get everything in place for new owner to do it.
You can make the finish and interest of a house way more wow through changing the styling—and that way you can bring it with you! New couches, some new lighting (big, modern, dramatic), new rugs, new artwork for walls—not telling you to actually buy a Rothko but look at these sort of scale pieces where you can put a modern couch underneath and scream “design”. Likewise groupings of matching paintings—e.g. 3,3,3 under each other—over a couch or dining table. Things need to be the right scale for the house—it’s large with big rooms, you should be looking at hotels and other big houses for inspiration, not smaller houses.
The rooms are boxy so they need sensitive dressing—I would get a stylist/stager. Things like how you place furniture, pictures on walls, mood lighting etc make an enormous difference. A good stylist will create the focal points these rooms need.
Your master bedroom needs to be pumped up—get a stylist and give them a brief life hotel sexcation, you want it to scream luxury in a kind of “dramatic, luxury hotel where rich people go to shag” kind of way. bathroom: in a kind of marble and mood lighting way. I would spend a bit of money on this bathroom with a similar brief—I think your target audience (you mention footballers!) would love this.
Your styling needs to pump up the drama a bit and to get a luxury feel without a lot of colour, you need to think TEXTURE and introducing some large objects of scale. You want areas in each room that grab the idea and give you a glamorous magazine moment—like a couch under a fabulous painting where you’d want to get your picture taken at a bar, that kind of vibe. Your house is big so it can absorb it. I’d love to see what a stylist would suggest for the hallway—I think it needs something oversize like a big lighting feature to pump up the drama.
In terms of colour, you need to kill the yellow—it doesn’t work. Yellow is good in period homes for a luxury look but I don’t get it in this context. It’s also a divisive colour. An interior designer could help with the palette, bun anything yellow!
Wait you have loads of books? Stage a fabulous home library room, make it a little fun and over the top—not a space for reading necessarily but an incredible executive study or somewhere fun for drinks parties. The kind of family buying this will likely be working from home and in a very senior post, a library study that screams “yes I am very important professional with large penis” might be a good selling point but easy to do.
Don’t touch the hot tub, yes many people will hate it but they’re not your target market!
For the garden I would get a landscaper and ask them what’s the highest drama planting scheme we can do with shortest bedding time and lowest price. We want to give the garden a less body shape, hide the boundaries, create a “wow” entertaining space (for a photo!) and pump up the drama.
Front of house: get the drive cleaned (in general you want everything to look as new as possible!) and maybe a few dramatic glam plants like white hydrangeas in pots? I wouldn’t go for colourful plants too much as they scream suburban semi, you want white hydrangeas, white or red roses, those weird dead Bush things that are all over Instagram.
Do mention the annex—can be sold for multigenerational living or as a staff/guest house.