What do I do if I don't believe financial disclosure?

VyEu

For a start solicitors don't cost 200k even if you do go to FDR (second hearing in financial remedy proceedings) unless the hourly rate is something stupid and there's a lot of unexpected issues, but putting that aside. 
1) have you got the backing documentation i.e. one years bank statements (or more if good reason to get those) up to date CETVs of pensions?
2) raising questionnaires would be the next steps. Nothing stopping you asking questions even at mediation
3) what type of pensions do you have. A defined benefit scheme is not the same as a defined contribution one and if you really want to see what each is worth, which I would recommend given your ages, you need a pensions report i.e. get an actuary to give you a split of pensions to provide for equality of income on divorce. 
4) take a view on the 'collectors items'. Idk how real they are, but what steps did he take to protect them? Insurance? Mentioned in the Will?

Ultimately it's up to you but unless it goes to court he can't be forced to do anything. If there are other bank accounts there if I were you I'd insist on form E full and frank disclosure, followed by questionnaires and if he's still not being honest, go to court.