@Inftsouthwest
I've been down the bursaries plus academic scholarships route with mine, and still it involved sacrifices. The usual old standards: no flash holidays, pretty much no "abroad" except France on the cheap, or in UK (yes I'll admit it, "second home"), ancient cars.
You want to send your daughter to the same public (or private) school you attended. Even if your parents paid full fees for you, you (and your parents) surely must at least have heard of scholarships, and bursaries?
The milieu you describe living in - all rich (or, as you say, "wealthy"), all public school - they should be able to advise you, having heard about (or even met, or even know well) children on bursaries and scholarships, and the parents of those children?
The fees you mention, £25K PA, are pretty reasonable. Perhaps the school has a trust fund that allows it to keep fees low, and in that case your confidence that it will never go under is probably justified.
You can definitely afford the fees, especially if you remortgage, even if you don't. In my case, I used inherited money, disclosed to and agreed with the Bursar as a payment plan over the (long, but wonderful) years, which was equivalent in value to selling or remortgaging.
If you want the school in effect to give you money, you have to be transparent about your assets and income, and major expenditures. You have to fill in the forms. You have to establish a respectful but friendly relationship with the Bursar. You know you can't just say "I want discount, so gimme discount."
You're unlikely to get a bursary because of your income. But whether you're successful or not, to read the post in which you said you would use the money you "save" (by taking the school's money, other parents' money!) to give your daughter special experiences, or something, I found repulsive, frankly.
For an academic scholarship, obviously it will help you if your daughter has academic ability and shows the potential to bump up the school's Oxbridge success rate. But that would be at secondary school level, and it sounds from your posts as if she's much younger than that, possibly pre-prep?
If she is still quite little, this is what I suggest you do:
From your posts, I'd guess you live in what some people on Mumsnet call an "affluent area"? Make plans now to get her into your local (no doubt charming) state primary school.
Girls' public schools intake is at age 11 (unlike a lot of boys' schools, whose intake is at age 13, which you already know, of course). Meaning that she won't necessarily be "behind" at intake.
Make an appointment with your chosen school now - ask to meet with the Admissions Tutor to talk about secondary age entry. Ask what level of achievement the school expects at age 11. Do they expect French? Ask if there's an entrance exam? Presumably there is?
Use all that lolly you'll have saved on pre and prep fees not for "special experiences" but to hire a tutor recommended by the school (if they will recommend) or ask your rich public school pals for recommendations.
But, OP, I'm afraid I'm going to be that horrible, awful person now.
You're making a ton of money, so well done you.
That aside, you've come out of this supposedly wonderful public/private school using "Me" as the subject of a sentence: "Me and my brother went", "Me and my ex recently split".
Is any of this real? If it is, and that's really the school you're hankering after, it ain't worth it.