And now I'm being criticised as I want the financial information to be sent to my solicitor so she can advise me before mediation. I don't understand his pension (he has bought property with it) or his accounts to take a view on how much his business is worth
The fog slowly clears... I suspect he's been stalling because he doesn't want to reveal his finances. It could be that he has far more funds than he's let on to you and he's been moving/hiding his assets.
You would be ill-advised to engage in mediation in respect of financial matters without having all of the facts and figures at your disposal. Your solicitor/yourself should be given sight of his Form E so that any questions can be asked before mediation begins
With regard to your petition, as others have said, he doesn't have to agree with the content and, if he doesn't sign and return it, you/your solicitor can apply to the court to deem it served and the divorce will proceed.
If you have any reason to believe he may have megabucks stashed away, employing the services of a forensic accountant could more than offset the cost.
Don't enter into any direct communication with him and let your solicitor deal with him in the appropriate manner. If he attempts to harangue or otherwise interrogate you simply go grey rock and tell him to instruct his own solicitor.