Joint offset mortgage account, how do I protect myself from ex ?

[Despair9]

Husband of 9 years father of my 8 year old dd left 2 days ago after saying he didn't love me any more and didn't want to continue, I then found out he has OW.
So now in action mode. Main issue is the mortgage is joint and we have offset account. I work full time so have regular monthly salary going in, he runs his own business so very sporadic payments, sometimes salary sometimes dividends.
Since it's joint I can't do anything without him seeing and vice versa, but main issue is I don't know if he's filtering money off from his main business and not putting into the joint account.
What's the best way to protect myself?

[LauraBridges]

Probably to see a solicitor. I am afraid it is dead easy for the self employed to pretend they have no money on divorce and if that is so you may end up paying him maintenance not vice versa if you earn more. Are you going to be able to afford to remortgage and buy him out his share of the house?