PS:

I also offered him joint-custody of dd4 in exchange for my joint custody of the other 3.

He said no, and when I agreed to go to mediation with him, he phoned me and told me he wasn't prepared to compromise with the mediator, so I didn't go.

I have asked him to involve me numerous times and he just said when people separate they don't parent together anymore. The absent parent has whatever visitation the custodial parent says and the custodial parent makes all the decisions to do with raising the children.

To give you an example, last March when it was dd1's 9th birthday, he organised a birthday party with all her friends and their parents.
I was not invited and I only found out because dd1 told said

'I'm having a party but dad says I can't invite you'

I challenged him about it and he just said he didn't think I would want to come because he lives in a different town.
This was when the dating was going great, too. It's on one of my old threads.

He also refused to let me know where dd3 was going to pre-school and wouldn't allow me to go there, so I am sure you understand now why his remark about going to dd4's pre-school made me so angry.