My ex an I got a “deed of separation” drawn up by an online solicitor
It set out what we had agreed on paper – I’m not sure how much the document is worth in legal terms, but it seemed like a step in the right direction
Then after 2 years we had a DIY divorce – except for the money bit, got another real (online) solicitor to do that, again based on what we agreed between us
You could skip straight to the divorce – but you will have to agree who will take the blame (for adulatory or unreasonable behaviour).
Take a look at the wikivorce website – it’s very good