Seperation advice

Hi all. My husband and I are considering a trial separation, but I'm not sure about the rules for who I need to inform if anyone? We live in a council flat and I am due our 3rd baby next month. Due to this he will be staying at the flat with us to help out with the transition and the kids for the first couple of months, and then he will be staying at his mums for the foreseeable. Is it a case of me advising the council we are separating and then keep them informed of our final decision once the chaos has settled down after baby? We have agreed that he will no longer contribute towards the bills as primarily it will be my home for me and the kids, and he will be helping me with childcare and the general running of things so I will be left with double the outgoings I have now on top of SMP, so to say im a little overwhelmed is an understatement 🙈 Thanks in advance for any advice you can give me!