To ask DH to continue to work

Your DH is burning out. I’m sure you love him more than your lifestyle. Live in the country (we have private schools there too) and visit London. Your DH deserves to enjoy life too.

I think you need to look at the risks. If he is very stressed and unhappy he could become very unwell; and that would have significant impact on the whole family. If you downsize would he potentially retrain or do you have a career that you would like to develop? Maybe accessing some coaching and financial planning could help in terms of working out mutual goals

Probably the most selfish post I have ever seen.

Ah, I cross posted with your latest.
If there is really no mental or physical illness going on then regardless of where you live I don't find it acceptable that one partner unilaterally decides not to work anymore (totally different if it's a joint decisions). But there is still a discussion to be had over where you live. I wouldn't like to think of my dh living somewhere he absolutely hated on my say-so.

Is your DH’s job funding your current lifestyle, OP? I think you may have implied that but I am not quite sure.

Your DC sound rather young, so I am guessing you haven’t lived in this (lovely sounding!) house all that long. Are mortgage payments significant? If DH’s job is funding tuition for at least 3 private school places (because they ‘all’ attend such) on top of the mortgage, he presumably has a high pressure job.

I believe that you do work hard at your job and as a homemaker in the most profound sense of the word (and that this job, done well, is vastly underrated) but the pressure is not the same. As @InBedBy10 said, a weekend cottage on top of all this does nothing to ease the pressure on DH.

As I understand it, YABU. DH deserves the same chance as you to find life satisfaction. You can stay in London considerably more economically, you can increase your own financial contribution, you can embark on a new way of life. You have lots of agency.

Is there a middle ground?

The 'why' is crucial here. Maybe he is burning out and needs the move for mental/physical health issues, maybe there are financial reasons he can't sustain the London house, the private London secondary schools, the open house for friends and relatives from all over the world.
I don't think I would be stamping my size 5s and demanding he continue to fund a lifestyle that would leave him ill, bankrupt or hating all the extended family and friends.
I'd be getting to the bottom of the 'why' and that in itself might throw up some compromise solutions.

Well you earn the same as him and then you get to decide.

It sounds like he is finding being the main earner difficult and you are the the only one happy with the situation at the moment.

You can't sustain your current lifestyle on your wage alone. So there needs to be a chat about moving forwards with a lifestyle that is affordable and happy for you both.

Yes, the crucial bit you've missed out OP is why DH wants to move and what that has to do with his job.

Your current post is summed up as "I like where I live and have a lovely life but DH wants to move and I don't". YANBU to not want to move, but you haven't explained why DH thinks you (the family) should.

YANBU, selling up and moving a whole family from London into the countryside is a massive decision and a huge change in lifestyle. You all need to be on the same page. Lots of people do it and live to regret the decision because they can’t afford to move back to their previous standard of living.

Talk to your DH and find out more about what he wants and how you might be able to compromise. A weekend place in the country might be an option though it usually becomes a total pain packing up for the weekend and driving through the traffic both ways.

If you live in central London would you be up for a move a bit further out where there is more green space but still within a short commute of the city?

Exactly. Then OP says that she does work.

If you tell the truth, you don't need a good memory - Judge Judy

Would the move mean your DH can afford to retire?

If he can afford to retire, then you kind of need to go along with it. That’s the problem of being reliant on a man for money, married or not.

Your lifestyle is very much dependent on your DHs job. Have you discussed and considered that he might be under significant stress and pressure to maintain school fees and living in London. Sounds like he has reached a tipping point where you both need room sit down, reevaluate your priorities and consider options.

"I am happy and content with the life I have worked so hard to create for our family."

Seems like this lovely life is paid for by your husband working hard though?

Not to diminish the value of your domestic labour and childcare but it is interesting you see your lifestyle as being created solely by your own hard work (no mention of your husband's input).

If he wants to reduce costs (perhaps he is well aware that he isn't going to be able to continue to earn enough to maintain this lifestyle) then you can reduce costs without having to move to the countryside. London has many great state schools and you can downsize homes and do without a guest annex, perhaps even in a slightly less fancy neighborhood

Your post title is misleading. Will the house move mean that your DH can give up work? Is it the moving out of London or DH giving up his job that you disagree with or both? If you want to stay in London, can you get a better paid job so that he can step back from being the main earner but still stay in London?

You haven't explained yourself very well. The title of your post suggests your DH wants to give up work but the text suggests he just wants to move. Do you mean that if you move out of London he can give up work and live off the proceeds of sale? You need to clarify.

Does he want to stop working altogether? Or get a different job?

Is your current lifestyle dependent on your h carrying on in his current job? is he happy in his current work? presumably not if he wants a lifestyle reset?

Lol. You're having us on aren't you?

Do you have a choice realistically? It's your husband work that is enabling your lifestyle. You can't afford it without him and you can't force him to keep working in this job if he doesn't want to. He isn't intending to stop work and plunge his family into punary, is he? He's suggested a perfectly adequate lifestyle for you all, which I get isn't your preference, but unfortunately you (personally) need to cut your coat to your own cloth, because its not OK to force a partner to work because you want to enjoy a particular standard of living you cannot afford. Could you downsize and stay in London as a compromise?

YANBU for not wanting to move. I think alot of people idolise country living but the reality doesn't always live up to the fantasy. Especially if you're used to city life.

Is he stressed in his job? You have a large house and kids in private school. How is buying a weekend cottage going to ease the financial burden on him? Its not fair to expect him to stay in a job he hates to fund your dream lifestyle. If that is the issue.

There is a compromise here. You don't need a big house with a annex. Would downsizing to a smaller house in London ease the pressure on him?. Your friends can sort their own accommodation. Your children don't have to be in private schools either. I'm sure there's lots of other ways you can cut back so you can stay in London.

I don’t think either of you are unreasonable. But if it means uprooting the DC’s education I’d be inclined to agree with you and stay put until youngest has finished school.