Make sure your lawyer utilises a forensic accountant because serial cheaters waste a bone chilling amount of marital funds. You’re in the UK, they have forensic accountants for this purpose and your lawyer will be able the draft your paperwork accordingly, might even help with negotiations around support and spousal maintenance.
Next make sure you both download a parenting app and every single correspondence about the children go through that, your lawyer will know the best ones to use. Never ever respond outside of this app, no calls no emails. It’s the one thing you should be vigilant about. Once you have set that up, block him and go no contact, he only needs to communicate about the children, you do not need to know if he is feeling bad or is sorry, if he wants a sympathetic ear he can look elsewhere. This is hard but the sooner you guard yourself from him and seperate your life from him the easier it becomes, if you wait, let him talk about anything other than the kids, false hope blooms and that is toxic stuff, he is a serial cheater, they’re not safe to be around, distance yourself.
Keep your plans about everything to yourself now. If you share your plans he will have an opinion or try and get you to do what he wants, what is in his best interest not yours, not the kids. Don’t share any plans, even if your lawyer comes up with a savage agreement keep a lock on it. Never underestimate what an ex will do with information about things you’re doing or want to do.
For day to day, lists, lists are your friends no joke. Get a notebook and keep it by your nightstand, when you wake write the days date and jot down the things you know you need to do, include the obvious to begin with like make lunches, shower, drink water, call XYZ to change accounts into my name, cancel XYZ, call mum etc etc and cross it off as you go. Divorce is distracting, disorientating and painful without the added trauma around infidelity, making lists get you through it. Doing activities with the kids helps too. You near the beach? Go there, go for a walk get some fish n chips, near a zoo? Spend a day there with them. Remember to talk to a GP if you’re having high spikes of anxiety or can’t sleep.
They can make as many promises as they want, but if they don't put action behind it, it doesn't mean anything.
I edit because I'm fluent in typo & autocorrect hates me.