Hello!!
I did it! That's my first step out the way. The solicitor was lovely actually, really understanding, friendly and knows her stuff - she knows the sort of character we're dealing with as well so I felt instantly supported and understood.
So, I definitely have a case for unreasonable behaviour grounds as we all thought! She agrees for my safety that I should move away to stay with my parents when I file papers as I am at risk - I'm also perfectly legally fine to take the kids away in that time to a safe haven with my parents and am under no pressure to bring them back to see him.
I will also be recommended for a non molestation order at that time too which is great as I will need to return to the house obviously for school.
She agrees me moving out of London, closer to my parents and having all the equity from the sale of the house to buy a cheaper property - but 1. He would need to approve this through court that I can move away from the area and 2. he would still have his share of the equity so when dd2 finishes full time education I would then owe him his share. She said rarely is the share 50% in cases like mine where he is more than full time at work and I'm at home with the kids or working my hours around them. I'm more looking at 65/35 or 70/30.
She did run through all outcomes - best to worst - best no contesting from him and it can all be wrapped up for about £5k
at worst he contests everything, it goes right through court and I could be looking at £55k
- this is not shared either - that would be £55k each.
That obviously is totally worst case scenario but she had to pre warn me - I think if that happened and it looked like it was just going to drag on I would just stop proceedings and I dunno live rented locally? Can cross that bridge nearer the time. There is also a risk with characters like mine that he may walk out of his job so that he doesn't need to pay me anything. Hopefully unlikely but these people are unhinged and unpredictable.
You hear things like that though and a fleeting thought comes over - this is scary, I could just forget it all - just try and be his friend and keep him happy, keep trying to snuggle up to him even when he's being both physically and mentally dismissive, try and sleep in the same bed as him and pretend it isn't excruciating, turn a blind eye to the moods and the scary atmosphere he's trying to create and the maniac driving, reckon to myself that the kids could do with better discipline than I can give - funny they behave so much better for him. But no, the thought of that is just unbearable - this is what a marriage that has broken down irretrievably looks like I guess and it would be a waste of precious life staying in it - no matter what it costs 
Next step is awaiting her letter detailing everything we talked about today which should be with me by Friday.