Single-family house 175 sqm without basement, too big?

Leave out the underfloor heating here for sure

I doubt that this has any effect. The room is simply heated through the other rooms anyway, as it is a thermal envelope overall.

You do not have to doubt that. With us, it is like that and in the pantry with the shutter closed it is already cooler than in the surrounding rooms

Thank you for the many inputs

Attached is a site plan. What do you think of the position of the house?
The brown area is a double carport with a tool shed, measuring 6x8 meters in total. The mentioned slope runs from northeast (high) to southwest (low) with a height difference of 4 meters.

Take a look at @hampshire's concept with a teenager. He gave his boys small apartments. I don't think the idea is bad.

However, the concept was also implemented on a property that is exceptional in several ways.

Our son has been living in a room with the shutters closed for about 6 years now (since he was 14).

How much does he earn during his training to be able to contribute accordingly to the electricity bill?

Our 20-year-old regularly leaves a pan or the stove on in the kitchen; I would never plan a separate kitchen and even a separate entrance for that.

I may have already mentioned that I recommend the anti-authoritarian upbringing for careful moderation.

The brown one is a double carport with a tool shed,

... and the blue one a carp pond?

It was not about the house in Hampshire, but about the implementation of 2 adults + 2 kids who are almost grown up

... and the blue one a carp pond?

Yes exactly and I am a carp. So it is supposed to be a pool, oval but not so ugly. Unfortunately, the program didn't offer more.