England & Wales separation: do divorce, children and finances all happen in one process?

No. GOV.UK treats these as separate issues. You may need to deal with the divorce itself, arrangements for children, child maintenance, and financial/property arrangements separately. If you agree, many parenting and financial issues can be resolved without a court hearing, but court orders may be needed to make some financial agreements legally binding. Official source: GOV.UK Separating or divorcing. Guide: https://getinstantlaw.com/family-separation-divorce/what-to-do-first