I've read your previous thread and this one too.
He really is something. A bit dim too but he really is something. The bunch of flowers! I mean really?!?!?
I would recommend keeping your powder dry for the time being. Get yourself the best divorce solicitor that you can afford. Borrow money if you have to (you'll be able to give it back in the end) to get the best solicitor you can for this.
Take every single penny, cent and pound that you are entitled to. That your children are entitled to.
I agree with the person who suggested getting paper copies of all of the important documents. You will need to keep a cool head on your shoulders now. I realise that you're emotionally still raw from the events that have landed in your lap but (and I don't mean this harshly) you can can cry later, mourn for the relationship you'll never have with him later, your kids need you now. You need your wits about you so that you can be the strong capable woman that you are.
Look after yourself. Treat yourself with kindness. This cannot be an easy time for you or your kids.
For the time being, I would, at the very least, only agree to use an intermediary for the children to be handed over. He cannot be trusted (based on him approaching an estate agent being the latest evidence of this).
Think of it like this - you need to don your armour now as you're going into battle with a piece of shit and you need to protect yourself and your kids. He's it his network/army (her, his mother, the friends at the golf club to name 3) and you have your troupe too. Keep strong and you will get out of this as a stronger, more together woman.
I love this poem and I hope you find strength in the words that Maya Angelou wrote: www.poetryfoundation.org/poems/46446/still-i-rise