Ladytink, it would be a good idea to discuss the petition with a solicitor. However maybe you need to get some counselling to help you to come to terms with his decision to divorce.
From your previous posts you are very determined not to divorce and had already tried relationship counselling to help save the marriage. The upshot is that it didn’t work for him. He is an adult and he can make the decision to end the marriage. Even if he is wrong, you should respect his decision that he wants to end the marriage and the relationship. Unfortunately this is one of life’s unilateral decisions even in a marriage.
Do you think fighting the petition will make him any less determined to be divorced or that he will view you as less unreasonable? I expect it will have the opposite effect. It will reinforce his opinions and belief that the marriage should end. That’s how I would react in his position and it would convince me that I was doing the right thing.
Current divorce laws mean that fault must be established or you face a long wait and period of separation. He needed to establish grounds if you were unwilling to do this. He could just have cited a list of random examples or used real life examples. I don’t know if that is the case. He could have made up a load of rubbish to satisfy the process or to highlight his view of you.
If your desire is to save your marriage, behaving unreasonably and refusing to respect his decisions, is not going to help and will make matters and life worse. You and your children will remain in a limbo without proper financial support and with a growing acrimony between you and your now ex.
Do not use outdated divorce processes to save your marriage. It will cost you money and add to your pain.