Would we be mad to buy a home and knock down a perfectly functional extension?

I wouldn't take that on.
Find another house.

Lots of people redo older extensions especially ones which are badly built, badly insulated and or do not give the required space or aren't well integrated with the rest of the house. Just demolishing it without replacing it with something else is probably less common.
If it's well built and newish then you may be better off looking for somewhere else.
The value may not reduce as much as you may think as you are really often paying for location and number of bedrooms.
It will cost to remove it though and you will need to install new windows. Check to see if you would need planning permission and/or building regulations.

Going against the general opinion here, is this your forever home? If it is, I’d buy it and do whatever you want to it. If you plan on staying there forever, does it depreciating in price really matter to how you want your home? You’ll know in your gut if it’s the right thing to do x

Not only is it maddeningly wasteful, you're in for an utter nightmare of costs if you want to rebuild that space with a more traditional look. Good luck with the planning permission expenses alone. Not to mention the building supplies and maintenance.

YANBU The extension doesn't make sense. I can't imagine what they were thinking building a weird room around the kitchen thereby containing the kitchen and making it windowless. It's actually ridiculous and there is no way I would be able to live with that.

However, I don't think knocking the garden room down is the answer. The obvious thing to do is remodel from the inside. It's the internal kitchen wall between the kitchen and the dining space which seems to be biggest problem. That's what needs to go imo. It's hard to imagine what it's all like without pics, but I'm assuming the kitchen is fully done etc so this would be a crazy expensive route. If the units are nice, you could still use them.
If this was mine and money was no object, I would lose the internal wall completely at the side return, but maybe make a nice orangery type space across the back, keeping the differentiated space and definitely not having weird glassless kitchen windows.
Is the house listed or something? I can't work out why they've done this. Maybe they weren't allowed to remove the original walls?

It's a shame, but I have to agree that this is one of the most stupid extensions I have ever seen and I don't blame you for trying to find a solution.

I really like it! I think the extension looks nice.

If you can afford it then I don't see a problem with knocking the modern bit down. If it makes you feel better I knew a couple that knocked down the entire house (modern) and rebuilt on a different side of the plot! A huge proportion of a house cost is the land it sits on anyway.

I think it’s up to you! If you can afford it and it’s your forever home, why not?

It would be a shocking waste to knock all that down. Find another house.

Can you do as others have suggested and remodel the kitchen so it becomes part of the extension? I agree that the kitchen looks a bit odd

Agree!!! OP you would be mad to knock that down. Buy a different house and leave that for someone who will appreciate it. Such a waste .

If it's the house posted then it's Grade 2 listed so not so easy to just start knocking stuff down.

I think it just needs a rejig.

have you thought about fully opening the space where the big chair to the left of the Aga is, and then closing/ putting a glazed door where the existing large opening is.

The bate brick walls of the bathroom don't do it for me tbh

If the house is the one on the link someone else posted above, I definitely wouldn't knock it down. What a nice space, could look amazing with the a little creativity and the right furniture. You would be wasting thousands knocking that part down I feel.

You’d be bonkers to get rid of it. The extension room itself is nice. I admit it means the kitchen is left looking a bit odd……you may get used to it…..think of it as quirky?

If not could you look at knocking it through? I assume the wall is load bearing but maybe something can be done with beams? Have one massive open plan space with the kitchen at the end nearest the original house and then seating and dining area near the windows?

The extension looks fine. No, I wouldn’t knock it down

If it's a forever home, then it would be costly but not ridiculous to replace the extension with something more to your taste.

It would be totally ridiculous to just pull it down - it would cost a significant amount simply to remove space and value from the house.

It's a beautiful house and I disagree that the extension looks awful To my mind the whole place looks fantastic!!

@fanaticalfairy - it looks 'sparse' because there isn't much furniture or colour on the walls

As others have said, it’s too much property to lose and a colossal waste of money. If you buy I would look at living in it for a while and think how you can rejig it to make the space work better.

The whole property isn't nice.

Too .. sparse

https://bakerwynneandwilson.com/property/pinnacle-farm-coole-lane-newhall-nantwich/

In all honesty unless there's structural damage I would accept that as part of the house now

I think you'd be mad to knock it down and lose all the space. But you could refig the space and have a long term plan to build a much better orangery instead.

For example, how about putting back a window in the gap and filling the extension with LOTS of plants (the Victorians were very keen on conservatories of ferns etc) so you barely see the structure. Add some little patio tables and treat the space as part of the garden.

Yes I'd def take it down. The number of modernised old houses you see is depressing - if you wan't to live in a quaint old house then live in it don't add bits so it's just like a modern house.
There's a little cottage near use - it had 1679 in the stone over the front door - it's been bought had huge wall window put in at the front left and a big flat roofed extension at the back, a modern garage in front. So sad