[0] https://en.wikipedia.org/wiki/Constitution_of_the_United_Kin...
[0] https://en.wikipedia.org/wiki/Constitution_of_the_United_Kin...
The Constitution of the United Kingdom or British constitution comprises the written and unwritten arrangements that establish the United Kingdom of Great Britain and Northern Ireland as a political body. Unlike in most countries, no attempt has been made to codify such arrangements into a single document, thus it is known as an uncodified constitution. This enables the constitution to be easily changed as no provisions are formally entrenched;[2] the Supreme Court of the United Kingdom recognises that there are constitutional principles, including parliamentary sovereignty, the rule of law, democracy, and upholding international law.
You cannot point me to a document that is the constitution. Words like uncodified or "unwritten arrangements" just create a semantic whack-a-mole, furthering the point that no written constitution exists.
Honestly, a country can have a universally recognized and respected written constitution without "everyone agree[ing] on it." See United States of America, Constitution Of.
It makes the constitution some abstract thing, rather than a very factual set of rules, which you want the constitution to be.