> repealing the original laws and replacing them with a single law that covers everything in one place. Legal refactoring if you like. I can only imagine that would be a humungous task. And presumably the existence of case law makes it much harder still.

These are called Reform Acts. They are indeed humungous tasks, rarely undertaken. Where I studied law, in the Northern Territory, a Law of Property Act was passed in 2000 and repealed Acts and overruled case law going back to the 12th century in Britain. It was indeed a massive effort.

For some areas of law the Act is also a Code (the Act explicitly says that it is the sole, whole body of the relevant law). This is mostly done for criminal law.

Codes are rare in common law jurisdictions like the US, UK, Australia, Canada, New Zealand etc. Codes are much more common in civil law countries like France, where the ideal is for all of law to be centralised and rationalised. Both systems require endless tinkering, debate and reinterpretation, which is why I am skeptical of universalist missions to convert the whole of the law into a system of formal symbols.