Hi,
See a solicitor, file the divorce petition, also file an application for financial relief. You can get your solicitor to draft some very vague reasons. The least offensive the better really. Your stbxh will get a notice of the court hearing date for financial relief. In my case, the divorce was not granted until financial relief had been settled. Take the original of your marriage certificate to your solicitors appointment. If he contests the divorce, ultimately it will just take longer and cost more, but the outcome is the same in the end.
When you file for financial relief, your stbxh gets sent a Form E to fill in, as will you. This is a declaration of everything you have, house, life insurance policy, pension, savings, businesses, stocks, shares, piles of cash, valuable assets, debts - everything. While you wait for the form, get busy at home getting copies of everything you can financial.
The same form asks you what your interest is. It is at least 50%, but could be more if the children will live with you permanently.
I did not have a custody battle, so am short on advice on that front. Everything child related was mutually agreed, and there is still nothing court ordered today. If my exh steps out of line or breaks the mutual agreement though, I'm sure he is under no illusions about how quickly I will file for a court order, so to date all is well there. But child arrangements is part of the same process of divorce. In short, there can be no divorce until what you agree on with regard to how to share the marital pot and how to care for children is filed with the court. If you don't agree, the court will decide for you, and all agreements or court decisions will be written up in a court order in the end.
Remember, it is solicitors time that costs the most money, so the more you can agree between you, the better. You may well be asked to use mediation to come to an agreement, it will still result in a court order, even if you don't attend court.
Best of luck, I can't tell you how much better I feel now it is all done and dusted, even though I didn't want it in the first place.
Lost