Divorces, separating finances and arrangements for any children are dealt with separately. In England & Wales the actual divorce isn't too complicated and if you are prepared to do some reading and research the cheapest way is to do it yourself. Application form D8, guides D183 etc and the list of court fees EX50 are all available to download from the Ministry of Justice website. Books Which? guide to divorce and the Family Court Without a Lawyer by Lucy Reed are useful resources to read.
Care needs to taken filling in the forms as some people have difficulty amending the form and there are fees for this. Doing it yourself is a false economy if you have to pay to amend the form as there are solicitor online divorce services that will do the divorce for around the same price as the court application and amendment fees.
Pitfalls to avoid are wording allegations for unreasonable behaviour in such a way that it inflames the situation or too mild so the court doesn't grant the divorce. If emotions run high it makes negotiating any arrangements for separating finances and children difficult and complaints of unreasonable behaviour should be serious enough that it is intolerable for you to live together.
If you can't afford a solicitor and there is a dispute about arrangements for children which can't be settled through mediation it normally isn't too complicated to do it yourself either. There isn't a great deal of law involved and most of the issues are every day parenting ones.
Settling finances is more complicated. Even if you are divorced either spouse can potentially make financial claims against each other in the future unless there is a court order separating the finances and dismissing future claims. It isn't possible to understand the s25 Matrimonial Causes Act 1973 checklist of factors and other law taken into account by reading.
When sharing the finances can be agreed most people (unless they happen to be a family solicitor) will still need a family lawyer to draft an order. The order is then submitted to court along with a financial disclosure. Once the order has been ratified by a judge the financial settlement is legally binding and enforceable.
Scotland has it's own legal system and the law is different.