If the Decree Nisi is through then it is best to apply for ancilary relief asap if you intend to - however, can you not make an agreement with your S2BX? Going down the ancillary relief route is long and costly. Don't dismiss it on the divorce papers though - keep that option open! Any solicitor will tell you this - if you close off that avenue at this stage you will not be able to go back on that.
Hope this helps - Attilladahun on this site is very helpful...
Fee, given the circumstances and the former husband's approach, it would make sense to apply for ancillary relief, just in case. You can always drop the action. But it sends a strong message to your former husband to negotiate a reasonable solution, or face the consequences. Strikes me he wants it all his way. You are still the primary carer for your children and the significantly lower earner. You are entering this stage in your life at a significant financial disadvantage.
Best of luck and keep posting