I see it's been a couple of weeks @hellwithadrunk so hopefully you've got the advice you need, but in case not...
AS ALWAYS, THIS IS ONLY GENERAL INFORMATION ABOUT ENGLISH FAMILY LAW AND SHOULD NOT BE CONSIDERED ADVICE ON WHAT YOU SHOULD DO - YOU SHOULD ALWAYS SEEK ADVICE FROM A SPECIALIST FAMILY SOLICITOR WHO CAN GIVE YOU SPECIFIC ADVICE TAILORED TO YOUR INDIVIDUAL CIRCUMSTANCES
When people get divorced (in England/Wales) the court has the power to redistribute your assets, and/or to order ongoing maintenance payments in any way it considers "fair".
Fairness is obviously in the eye of the beholder, but the court usually concerns itself with two key principles:
The first is that any wealth accumulated during the marriage should be shared equally unless there is a good reason not to ("sharing") - typical reasons people argue it should not be shared are that the wealth predates the relationship, was earned after separation or was received as gift or inheritance).
The second is that each person has various financial needs ("needs") that it is right should be covered by the couple's existing assets or future earnings. The most basic needs are to have somewhere appropriate to live and enough income coming in every week/month to survive, but the court can interpret needs far more generously if the money is there to cover it (the highest ever assessment of needs I have seen was £224m!)
Except in very unusual circumstances the court will say that it is more important to meet someones needs than to ringfence an asset because it is non-marital.
The parent that the children spend less time with will normally be expected to pay some child maintenance - unless they are very high earners this will simply follow the formula set out by the Child Maintenance Service. Quite separate from that the higher earner (regardless of who the children live with) might be expected to make regular "spousal" maintenance payments to the other until such time as the receiver is able (or expected) to be financially independent.
If that all sounds rather vague it is, because the law deliberately gives judges a huge amount of discretion in each individual case. That makes it easier to achieve fairness in any given case but difficult for anyone to accurately predict what the likely outcome might be (and is one of several reasons why I disagree with @GonzoFlyingProducts when he/she says that any old high street lawyer can help you - I cannot stress enough the importance of going to a family law specialist).
I have mentioned the court. You don't need to go to court and most people don't. It is just important to have an idea of what the court might order if asked because that is your "best alternative to a negotiated agreement".
There are several processes for actually working out the financial settlement: just the two of you sitting down together at the kitchen table and thrashing it out; using a specialist mediator to guide your discussions; using solicitors to help you negotiate (either through correspondence or structured meetings) or handing over the decision-making to a court or arbitrator. Whichever process you use, it is expected that you will each give each other full and frank information about your finances and failing to do so could allow the settlement to be reopened. Once you have reached agreement I would urge you to ensure that it is drawn up formally and submitted to the court for approval - your solicitor can help with that.
I cannot give you advice here based on the limited information you have provided except to say that it sounds like there is far too much money here for you to worry that you might have to walk away with nothing.
You will find it really helpful to look at the AdviceNow guide at www.advicenow.org.uk/guides/survival-guide-sorting-out-your-finances-when-you-get-divorced (don't pay £19 for the hardcopy, just click the link to download the PDF for free).
It sounds like there are other issues you will need to discuss with a solicitor, including:
- the divorce process itself
- arrangements for the children
- safeguarding the children
I also disagree with @GonzoFlyingProducts that amicable divorces are unusual. Plenty of people get through things in a (relatively) respectful way and many firms (including my own) are committed to helping people work through these difficult issues in as non-confrontational way as possible. If that is your goal, the worst thing you can do is pick the wrong lawyer - so make sure you pick someone who is a specialist in family work, is used to dealing with your level of assets and who sends a clear message that they try to deal with things constructively. The Find a Member search at www.resolution.org.uk/findamember/ would be a good place to start if you can't get any personal recommendations.
Wishing you all the best.