To ask you about conservatory

No idea, you need to get some quotes from builders. Even my partner who builds for a living can’t answer that without seeing the scope of work in person.

The estate agent's description is just words. They usually explicitly say you can't rely on the description.

That is either an extension or an incorrectly built conservatory.

To me that's not a true conservatory. It has half brick walls and only one row of glass (plus the roof).

Something to consider is the sound when it rains. My parents conservatory is really loud and they're glad of the door being able to close.

To me that's not a conservatory. They do normally have internal doors. This would be more of an extension.

Was the one you linked to part of the original build? It looks like next door's is identical, so assume it was designed and approved as a new build meeting all the relevant legislation.

Ours is open to the kitchen and does not have building regs - our vendors bought an indemnity policy as part of the sale, as did the previous owners when they sold.

Have to say it's not ideal as it does get cool in winter.

We had a conservatory fitted WITHOUT doors OP! We contacted several conservatory companies and none had ever done this- because it required building regs. We organised this separately to the conservatory company via the council, but it can certainly be done! There were fees involved with this though.
I'd recommend getting orphan, brick walls where you can. It helps to reduce heat loss. We chose the best, most insulated ceiling glass they had. For various reasons, we were only there a few months before moving, so cant comment on all seasons. It did, however, get very hot and glary on a sunny day, and chilly at night- despite being such a new, modern conservatory! I'd swap for more of an insulated roof- so essentially an extension if possible! Maybe with 1 or 2 glass panels instead of the whole ceiling. The one in the real estate brochure you showed has opaque glass- which might help a bit too, but depending which way if faces, I'm sure it too would get very hot.

Yeah, too hot in summer and too cold in winter. I did something similar with an extension and it wad unbearable.

Conservatories are exempt from building regulations if they have an external wall separating them from the main house. You can absolutely build a conservatory like in the pictures but it will have to comply with BR and you will need to get in signed off by building control. The builders either don’t want to bother or there are structural limitations to your property. Essentially, this will be an extension which will need changes to fundament, cavity insulation etc and will be more expensive than a regular conservatory build.

We have a conservatory at the back (which came with the house). It gets incredibly hot in the summer - we've recorded over 50C with the windows and doors closed. It then gets really cold in the winter - our boiler is generally more than sufficient for the house, but if we've had the doors to the conservatory open (for a larger gathering) we've had to run the gas fire as well as the panel heaters in the conservatory itself and the central heating. I would never put one on without a door between, though I've seen houses for sale with a floorplan like the one you've attached.

More to the point - er... I've just noticed the 'sculptures' in the front garden!

Hm hard to know how they've done it - maybe they've used more insulation than you normally have with a conservatory? Or possibly been done by a cowboy builder? This house hasn't had a survey done or anything, perhaps if you tried to buy it your survey would say it's not ok!

But your builders are correct, if you have a standard conservatory you have to have external type doors separating it from the rest of the house. I think you need it to not be on the central heating either?

Essentially it's because of why everyone always whinges about conservatories, boiling in the summer, freezing in the winter. It looks like you'd be roasting (excuse the pun) in that kitchen in summer.